Quiet hero.

The Man Who Knew Too Much: Alan Turing and the Invention of the Computer, by David Leavitt (Norton, 288 pp., $22.95)

IF you have ever needed reminding of a nation's capacity for ingratitude, the story of Alan Turing ought to do the trick. And if you have never heard of Alan Turing, that only proves the point. Born in 1912 into the cheese-paring and snobbery of Britain's colonial administrative class, Turing emerged from a traditionalist family and an old-school education with a wild, unorthodox mind, and a record of achievement that establishes him as one of the most important mathematicians of the last century. In not much more than one astonishing decade, this extraordinary individual would not only play a critical part in paving the way for the development of the laptop on which I am now typing, but also, through his wartime code-breaking at Bletchley Park, help ensure that this article didn't have to be written in German. His tragedy, and ours, was that there was too little in the way of an encore. Within a few years of his greatest triumphs, Turing was a convicted criminal, guilty of "gross indecency" with another man, an embarrassment, if not exactly an outcast. Not so long afterwards he was dead, a suicide at 41 with the help of an apple dipped in cyanide.

With the secrecy that surrounded Turing's wartime activities now lifted, the essential facts of his life are well established and more than adequately covered in this new biography. After walking his readers briskly through the early years, David Leavitt presents them with the considerable challenge of Turing's first major work, the catchily named "On Computable Numbers, with an application to the Entscheidungsproblem" (1937), a paper that was, in essence, the blueprint for the modern computer. "Computable Numbers" is, in Leavitt's words, a "curious blend of humbly phrased, somewhat philosophical speculation and highly technical mathematics," something, he concedes, that is "disconcerting" for the "general reader" (that's you and me) since, invariably, easier passages "segue immediately into dense bogs of unfamiliar symbols, German and Greek letters, and binary numbers."

Well, when it comes to navigating those "dense bogs," Leavitt is, in keeping with one of the tasks of this biography (the book is part of Norton's Great Discoveries series, designed "to tell the stories of crucial scientific breakthroughs"), a pretty good guide. As someone confused by an abacus and in awe of a pocket calculator, I admit that my knowledge of computing is, or was, practically zero. Alter a re-reading or two of the chapters devoted to Turing's "universal machine" and its revolutionary implications, this level of understanding had been raised to somewhere between hazy and confused: no small achievement, and a tribute to Leavitt's powers of explanation.

Leavitt is no less deft in describing Turing's critical role in breaking the Germans' Enigma codes. His writing leaves the mysteries of cryptanalysis less mysterious and, as a result, we can begin to grasp the remarkable intellectual feat involved in Turing's penetration of the secrets of Hitler's Reich. We'll never know how many Allied lives were saved by "the Prof" and his work, or by how many years his effort shortened the war, but Churchill never doubted its importance. Turing and his team were, he wrote, to have "all they want." And so they did. More material rewards were to prove elusive. Stinginess and secrecy meant that the only official recognition of Turing's achievements was a bonus of a few hundred pounds and a rather minor medal. So far as is known, he never complained, and, to the end of his life, Turing kept the secrets of Bletchley Park to himself. He and his colleagues were, said Churchill, "the geese who laid the golden eggs and never cackled."

But there's more to The Man Who Knew Too Much than formulae, ciphers, and the click-click-click of the device that savaged Enigma. While his efforts inevitably fall short of the portrait contained in Andrew Hodges's groundbreaking, and epic, biography, Alan Turing: The Enigma (1983), Leavitt nevertheless succeeds in drawing a wonderfully vivid picture of his shy, dry, brilliant hero, an eccentric boffin with chaotic, shabby tailoring, uncertain hygiene, an unsettling resemblance to Rudolf Hess, and a yen for long-distance running.

What works less well is Leavitt's tendency to treat Turing's homosexuality as a lens through which his whole life must be seen, sometimes ridiculously so. Thus in discussing a later work, "Intelligent Machinery," a paper focused, as its name would suggest, on the possibility of building a truly "intelligent" machine, Leavitt notes how Turing's strategy of opening with a summary of the views of those who disagreed with him "foreshadows the gay rights manifestos of the 1950s and 1960s, which often used a rebuttal of traditional arguments against homosexuality as a frame for its defense"--a comparison that is both accurate and pointless. A little later, we find "Computing Machinery and Intelligence," Turing's "most famous and in many ways most perverse paper," described as a stew of anxiety over gender and sexuality, a reading that might have surprised Turing, a man comfortable with his sexual identity in a way that was, as so often with him, years ahead of his time.

Perhaps this was inevitable. Norton boasts that Great Discoveries will feature "writers from diverse backgrounds." It's that dodgy word "diverse" that should set the alarm bells ringing and that explains, undoubtedly, why Professor Leavitt, who teaches creative writing and is best known for novels focused on homosexual themes (The Lost Language of Cranes, While England Sleeps, among others), was chosen to write the biography of a mathematician. The result, ironically, of his approach is somehow to diminish the horror of the unjust laws that largely confined Turing's sex life to an emotional wasteland punctuated by furtive rumblings and discreet trips abroad. Nobody will ever know why he chose to kill himself (there were clear signs that he was going mad), but it's impossible to imagine that the ordeal of prosecution and the humiliation of punishment (in essence, chemical castration) did not play their disgraceful part. That is not enough for Leavitt, who dilutes tragedy with absurdity by suggesting that the way in which Turing (a somewhat obsessive fan of Disney's Snow White) committed suicide was designed to deliver an erotically symbolic message: "In the fairy tale the apple into which Snow White bites doesn't kill her. It puts her to sleep until the Prince wakes her up with a kiss."

Oh please.

Mr. Stuttaford is a contributing editor of National Review Online.