Agatha Christie, master puzzler.

ON NOVEMBER 25, 2002, Agatha Christie's play The Mousetrap clocked up fifty years on the London stage. It's been performed there more than twenty thousand times, to audiences adding up to about ten million people, making it the longest-running show in theatre history. A few other long runs ended recently, so even if it comes off tomorrow it'll probably hold that record for longer than most people reading this will be alive.

Nobody's sure why it's lasted so long. Agatha Christie herself thought it might run for eight months. To start with, it didn't do great business. Then things picked up, and as long as people kept coming there was no sense in taking it off. It became a fixture, and then a tourist landmark, and then a national institution.

It opened to good reviews, but later on some critics' hearts hardened. A writer on the Guardian (where else) thought the space it took up might be better used for "daring, experimental or difficult" plays.

In the theatre listings in Punch, the tone of the comment changed over the years. "One of Agatha Christie's feebler thrillers now inexplicably in its thirteenth year", was the line in 1964. In 1965, it switched to, "Agatha Christie thriller". After all that time, Punch's chaps hadn't yet noticed that this was a mystery, not a thriller. And by 1984, it had slipped again to, "How long, O Lord, how long?"

Longer than poor old Punch lasted, actually. It never recovered from its spell as a Harold Wilson fan magazine in the sixties, and it rolled over and sank in 1992. The title's been revived since, and a British bookie might offer odds on the chances of The Mousetrap outlasting the current model.

In 1952, Agatha Christie gave the rights to the play to her grandson. The film rights were sold in 1956, but a film can't be made until six months after the end of the London run. But now The Mousetrap isn't just a piece of theatre, like Private Lives or Hay Fever, it's a part of London's landscape, like Tower Bridge or Big Ben. It's not easy to see why the run should ever stop. The Hollywood moguls can't be holding their breath.

On the strength of this, Agatha Christie would be pretty famous even it The Mousetrap was the only thing she'd ever written, like Margaret Mitchell after Gone with the Wind. On the other hand, she'd still be famous even if she'd never written a line for the stage. Her theatre career was like P.G. Wodehouse's, amazingly successful, but trivial next to the career in print

Most writers on Agatha Christie give lots of space to the curious matter of her disappearance for a few days in December 1926. They're sniffing after a red herring. Lots of people have gone a bit crazy and wandered away from things for a while. Only one person, though, turned out all those marvellously clever stories. How did she manage that? That's the real mystery.

She got off to a good start with The Mysterious Affair at Styles in 1920. In 1926, The Murder of Roger Ackroyd boosted her reputation. Still, between the world wars she counted as only one strong runner in a very strong field. She was an impressive performer, but so were a dozen or fifty others.

She delivered quantity as well as quality. In the twenties she published nine novels, five of them mysteries and four of them light thrillers. In the thirties she settled down to mystery production, and averaged nearly two novels a year. She kept up that rate through the war years, and after the war she eased back to a book a year until shortly before her death.

After the war the ranks of mystery writers were thinner. Some had stopped writing, some had changed their line, some had died. New recruits tended not to be mass producers. The survivors of the golden age between the wars were still the big names, and Agatha Christie emerged as the biggest of those.

For a while she was listed with Margery Allingham and Dorothy Sayers as one of England's three queens of crime. But she'd written three times as many novels as the one, five times as many as the other, and weight of numbers seemed to count. When she died in 1976 only Ngaio Marsh was still in sight, a fair way astern.

Lots of her stories have been filmed, mostly not too well. Recent television versions have gone better. Joan Hickson mightn't have been the best Miss Marple ever (Christie's family most admired Dulcie Gray), but she did please a big audience. David Suchet is the best Poirot so far, by miles, even if his moustache is a bit too small. But the Christie reputation was built at a time when screen versions weren't much help.

We used to be told she'd outsold everything in print short of Shakespeare and the Bible. Now it's said she's pulled ahead of Shakespeare, too. Nobody's sure what her sales add up to, but it's something in the thousands of millions. Those are honest sales, not boosted by school and university reading lists. Actually, the cultural establishment have mostly pushed the other way.

CHRISTIE FANS know all about the American highbrow Edmund Wilson. "Of a mawkishness and banality," he wrote after reading Death on the Nile, "which seems to me literally impossible to read." More anti-Christie argument came from Raymond Chandler, the hard-boiled private eye writer. "This is the type that is guaranteed to knock the keenest mind for a loop," he wrote after reading Murder on the Orient Express. "Only a halfwit could guess it."

Lately even British crime writers have come out against her. P.D. James, Ruth Rendell and Michael Dibdin let drive in interviews on television.

"There's no psychological subtlety," P.D. James explained. "This, together with the bland, undistinguished style, and the absence of any imaginative effort to evoke setting or atmosphere, means that for me she is a poor novelist, a bad novelist."

Ruth Rendell got straight to the point. "I don't feel that here I have a piece of fiction worth the name in front of me," she said.

"The kind of detective story she wrote," Michael Dibdin argued, "represents a grotesque perversion of the genre, and has had a disastrous effect on the development of crime writing in this country."

Commentators and critics always give her low marks for style, characters, backgrounds, atmosphere, truth to life. She's charged with having a poor attitude towards communists, the lower classes, foreigners and Jews. Well, everybody knows what commentators and critics mostly are, and this stuff obviously doesn't need to be taken too seriously. On the other hand, there's nothing wrong with treating it as it deserves to be treated, and turning on it, and knocking it to bits. Good exercise and good fun.

Bland style? Actually, that's just a mean-minded way of saying easy to read and easy to follow. Christie's prose is modest, economical, efficient and effective. Nobody needs to read a sentence over again to work out what it means. She doesn't tuck clues away in boring thickets of dense verbiage. All her tricks are done fairly in broad daylight.

At her best, she's brisk and witty. See the last few lines of Three-Act Tragedy, for instance. She's very good at dialogue, and the high ratio of talk to narrative is one reason why her stuff is so readable. It seems she was sounder on this than her publishers were. In 1968, she sent a stem letter to Collins, telling them to leave her spelling and her grammar alone. "I don't want sentences twisted round to be more grammatical when they are part of someone's spoken conversation," she told them. "Otherwise everyone's conversation would sound exactly alike and not like ordinary variable human beings ..." Editors are meant to make bad stuff better, but they can also make good stuff worse. This time, obviously, she was right and they were wrong.

Undeveloped settings? Obviously she thought her books were better off without heavy backgrounds. In any mystery, plot matters most, and the setting shouldn't get in its way. Readers might count a heavily developed setting as padding, and they might be right.

Undeveloped characters? But developing characters can count as padding, too. In a mystery novel, the mystery plot counts most. The story's there to carry it, and the characters are there to man the story. This calls for a victim, a detective, anywhere between three or four to ten or a dozen suspects, and a supporting cast of police, doctors, Watsons, lawyers, servants and so on.

The detective can't be allowed to draw too much attention away from the core of the story. The suspects can't be shown in too much depth, because one of them has too much to hide. In lots of cases, the character who's studied most closely is the victim, even if he's already dead when the story starts. But what we're told is all part of the puzzle, not character study for character study's sake.

A poor attitude towards the lower classes? No, she's just ruling them out as suspects, or weakening them as witnesses. In her books, no genuine member of the lower classes is ever guilty of anything worse than theft or blackmail. They're probably not bright enough to devise baffling murder plots, and in any case they're too busy at their proper work to put plots into practice.

A poor attitude towards communists? Actually, most of her on-stage communists are just silly trendies, noisy young men with heads full of nonsense. She never delivers any sense of the real, brutal, relentless horror of socialism. It'd be much easier to argue that her attitude towards the far left isn't nearly poor enough.

A poor attitude towards Jews? Some of her critics have pushed this line hard. In one early book, unkind remarks are made about a Jewish financier, but arguing that this shows she was anti-Semitic is like arguing that Conrad Veidt's dialogue in Casablanca shows the script-writers were Nazis. She put that bit in as a joke, sending up the style of routine thriller writers dealing with Jewish money men in those post-Marconi-scandal days.

Actually, it's a rule in mysteries that Jews don't turn out to be murderers. They can't be more than red herrings, and since readers know the rule they don't make specially useful red herrings. They're generally just mobile set decoration. In Agatha Christie's stuff, the worst any Jew ever does is to hope to buy a painting at a bargain price. In two novels the Jewish red herrings turn out to be the juvenile leads, getting the available girl at the end. It's possible to imagine stuff being a bit more anti-Semitic than that.

A poor attitude towards foreigners? In the Christie world, foreigners are mostly background figures. Like the Jews, they generally can't be taken seriously as suspects. If she'd really disliked foreigners, she probably wouldn't have taken on a hero as foreign as Poirot.

Who are the Christie murderers, then, if they're not servants or Reds or Jews or foreigners? They're people of her own sort, regular middle-class Englishmen and Englishwomen. They generally look to be nice, respectable, conventional, well-bred solid citizens, but it's their hands that slip the poison into the drinks. Does this count as prejudice? We don't find highbrows objecting to it.

Not true to real life? In the age of "magic realism", in a time when big book prizes go to stuff like The English Patient, that's not a wise charge to make. It's been claimed that private eye stories are closer to real life than fair-play mysteries are, but more recently it's been admitted that private eyes spend much more time snooping on straying husbands and wives than they do trading .45 slugs with mobsters. "The next private eye who solves a murder case will be the first" is the key line here.

Anyhow, as far as most readers are concerned, the hard-boiled private eye's world isn't true to life at all. Even in America, mobsters don't directly enter most people's lives. Agatha Christie's stealthy crimes among friends and relations are much more likely to start people looking sideways.

SO THE STANDARD anti-Christie charges are all junk. The crime writers' charges are just sour grapes. It must be tough, being so earnest and up to date, trying so hard, and then finding that your books keep on being outsold by such old-fashioned stuff, by somebody who isn't even alive any more. And if you're not much good at plotting puzzles, if it's too hard to do what she did so readily, then it only makes sense to argue that it's not the right stuff to do.

Agatha Christie wrote mainstream novels as well as mystery novels, and she knew which was harder. "I found with straight novels that they didn't need much thinking out beforehand," she said once. "Detective stories are much more trouble--even if you have no high ideals in writing them."

Robert Frost once classed poetry that way, free verse against formal verse. Formal verse was harder. Free verse was too easy--"Like playing tennis without a net," was the way he put it.

Fitting a mystery plot together properly is not easy. For instance, Presumed Innocent by Scott Turow has the bones of a fair-play mystery, but they're very loose in their joints. It's possible for a Christie-trained reader to work out the whole plot, crime, suspect and villain by about page 30.

The critics' charges are carbon copies of their charges against most other major popular writers. The thought police are on the job again, rounding up one more of their usual suspects. Anti-Semitism is just a smokescreen. Anti-socialism is the stuff they're really serious about. Writing off communism as a fad for silly kids is just as bad as showing it up as a serious menace. When you're doing your level best to destroy the civilisation around you, it's exasperating to have a nice lady pat you on the head and tell you that you'll grow out of it.

She always looks to be in favour of normal civilised values. Mostly they're just taken for granted, but every now and then a point's made in passing. "I have never regretted my part in bringing that man to justice," Miss Marple says in one early story. "I've no patience with modern humanitarian scruples about capital punishment." Hercule Poirot thinks pretty much the same way. "I have a bourgeois attitude to murder," he says. "I disapprove of it."

To a French speaker like Poirot, bourgeois is a fairly neutral noun or adjective. In English, though, it's a loony-left term of abuse, Progressive, committed liberal idealists might see this line as an unwelcome hint that non-bourgeois people might not disapprove of it, as long as it's the right people being murdered.

Every now and then, tough, bossy career women show up in Christie books, and they usually don't show up too well. "She was a great feminist and disliked men," one character says of another in Five Little Pigs. "Is that enough for murder? Surely not."

Feminists argue that if women are given the chance, they can do at least as well as men. Agatha Christie's record looks like evidence for that. She made a chance for herself, and she became the most popular writer in the world. She beat all the men writing in her field, and all the men writing in all the other fields. Not a bad effort.

Not good enough for the feminists, though. Instead of showing her off as an example, they play her right down. Feminism's a socialist movement, first and last, and it's only socialists who count. In feminist books on women writers, she gets the same sort of treatment she gets from jealous rivals. Endless regiments of Stalinist-minded university hacks score bigger shares of column space.

The feminists' line is crazy. Hostility from general academics makes a bit more sense. At least nobody can argue that she's really a credit to their side. She never went to university, she never even went to school. She was educated at home in Torquay, by governesses and by her mother.

These days, it's not easy to imagine any writer coming from a start as non-academic as that, never mind a world champion best-seller. What's the lesson there? Either her teachers were amazingly effective, or she was so terrifically bright that she could overcome any sort of handicap, or else, the less formal education a writer gets, the better. Professors with heads full of postmodernism won't find much comfort any way,

Really, from the cultural establishment's angle, the heaviest charge against her must be that she's a rather dangerous writer. Her stories aren't just amusing yarns, they're careful patterns of facts and lies. Which are which? She encourages readers to work that out. Like all fair-play mystery writers, she's teaching them to think about stuff. The more seriously they take her, the more thought they put into it, the more good they do themselves.

Critics and academics aren't too happy about that sort of thing. They don't think very well themselves, and they don't see why anybody else should think much, either. They've taken all their ideas ready made from mad, murderous, dead foreign dictators, and they've never questioned those, leaching people to question things strikes them as a bad idea.

Christie readers find that people often don't tell the truth about things. But truth does exist, and with a bit of trouble it can be found out. The establishment, though, think that the way to find the truth, or what ought to be the truth, is to shut up and listen to what the establishment say. That's all anybody needs to know. That's all anybody ought to be allowed to know. Measuring that sort of truth against the real, true truth can't lead to anything but trouble.

From their own practical point of view, the establishment are right. Their nasty ideas can't possibly stand up to a steady look from anybody who can think. When they attack her, it's really just in self-defence. It's bad luck for them that the huge majority of Christie readers don't pay much attention to anything they say.

IT'S MUCH, much more useful to look at the Christie readers own ideas. Why do they like her books so much? Why did they fall for them? Why do they keep going back to them? This is the sort of stuff those jealous rivals ought to be thinking about. For a start, obviously, the books really are well enough written. The stories are marvellous, and the style doesn't get in the way, and that's how readers like it. The brief descriptions, the extensive dialogue and the economical character stuff are all serious plus points.

The light touch and the flashes of wit are special plus points. She wants to entertain her readers, not to depress them. She doesn't treat murder as a joke, but she doesn't feel she needs to work to persuade them that it's not nice. She puts things neatly, and she turns the odd phrase. The characters joke with one another, even at points of stress, the way people do in real life. Modern female mystery writers are a grim lot, and they might think about learning from this.

The ethical background that the critics don't like is another big plus. Normal readers do think murder's a bad thing, and they're happy to see murderers caught and hanged. The middle-class settings let them escape for a few hours at a time into a world less grim than today's. The old-fashioned social ideas that put the critics' backs up are a relief from modern social engineering.

On a technical level, her greatest strength is her marvellous gift for mystery plotting, laying false trails, hiding clues in plain sight, getting readers to see things the wrong way round. Even the most seriously unfair critics will sometimes give her credit for that. Her average plots are superb by anybody else's standards, and her best are better still. Three of them (fans will know which) are unbeatable classics in the field.

Her name's a trademark, summing up a whole order of things, like Tarzan, Buck Rogers, Homblower. If you say, "Agatha Christie sort of book", then even the illiterate will have a pretty good idea of what you're talking about. By itself, it's a guarantee of quality, too.

Intelligent readers like her because they trust her. They know the game, they know she knows the game, they know she'll play the game. Clues will be tough but not unfair. No obscure bits of special knowledge, no rabbits out of hats. They're sure, every time, that if they pay attention, they do have a fair chance of getting it right.

To Christie readers, that chance matters. There's a difference between reading mainstream or crime fiction and reading mystery fiction, and it's the difference between watching a game and actually playing in it. That sort of stiff mental exercise isn't on offer anywhere else in literature, except in the best sort of science fiction. Not all readers want it, but readers who do want it know that Christie novels are where to find it.

As a mass producer, she has a special advantage over most other mystery writers. She takes up a lot of shelf space, and when new readers look for mysteries she's likely to be the first mystery writer they bump into. She gets to form their ideas about mysteries, and she's the one they measure the rest by. If other writers aren't as brisk and witty and ingenious, they won't like them as much.

In the long run, readers find she's got another big advantage over non-mass producers. She wrote so many mysteries, mostly set against the same background, and it's hardly sensibly possible to remember how each one of them came out. A normal keen Christie fan will recall the most famous cases, and ten or a dozen others, and then the rest will blur. Tackle them all in succession, seventy or so, and you'll start losing track before you're halfway through.

Five years on, how many solutions will you recall? Not too many more. So, time to be tested and fooled all over again. You can cycle through them all your life, and there'll always be some still out of focus. She can give literally endless pleasure.

WHY DID The Mousetrap trundle through its record run? Because it's the sort of play it is. It's not a great mystery play, it's not the best of hers, but it is a very solid one. It's well made, it's ingenious, it has a surprise ending. All those tourists see it as something terrifically English, a fine example from a genre that English writers have generally dominated. If it wasn't a classic of its kind when it opened in 1952, it is now.

Why is she the writer who dominates mystery fiction? Why isn't it somebody else? Weight of numbers, plus the right mix of qualities. For instance, Dorothy L. Sayers, Edmund Crispin and V.C. Clinton-Baddeley wrote fine books, but not enough of them. Ellery Queen, Rex Stout and John Dickson Carr were ingenious mass producers, but maybe they didn't match her in wit and charm.

The most interesting match is with Ngaio Marsh. There are lots of Marsh books, with good plots and Christie-like settings. They're thicker with non-vital detail, more like regular novels, less like straight puzzles. Many people would say Marsh is the better writer. Why doesn't she dominate the field, instead?

It looks as if pure puzzles really are what mystery readers like best. The rule's the same as the rule for science fiction. As far as intelligent readers are concerned, the farther the stuff is from the mainstream, the more specialised it is, the better it goes. These days, for some reason, most crime writers aren't much good at puzzles, and in self-defence they argue against them. But the best readers go on looking for them.

Pure puzzles put Agatha Christie at the head of the field, and weight of numbers and lack of trendiness have kept her there. She really was great. Her books are super, and people are absolutely right to go on reading them. For all sorts of reasons, they can't possibly read too much of them.