Master of the Game.

Spytime: The Undoing of James Jesus Angleton, by William F. Buckley Jr. (Harcourt, 305 pp., $25)

Bill Buckley's latest novel, Spytime, is a highly original work; indeed, one might describe it as a new kind of novel if Buckley had not already done something vaguely similar in The Redhunter, which was about Sen. Joe McCarthy. There is, of course, nothing new about historical fiction centered on real characters: What's unusual in these books is that Buckley writes not only about very recent events but about famous characters whom he knew personally, not so much romans a clef as romans en clair. When television and film sally into this, or at least into a neighboring field, the results tend to be labeled "faction" and frowned upon; but Buckley offers a significantly different, generally more authentic, and altogether superior product.

His protagonist, this time, is James Jesus Angleton. All that most of us may remember about Angleton is that he was, throughout much of the Cold War, head of counterintelligence in the CIA, a brilliant player in the global spy game, and that in 1974 he was abruptly dismissed. Why? The received explanation was that he had become dangerously paranoid, seeing spies, particularly in high places, where they did not exist. Other explanations were whispered-that he was the victim of political conspiracy, of anti-anti-Communism, of a Soviet plot, or even that he had been a Soviet spy himself. Buckley approaches this unresolved puzzle by following Angleton's career from youthful recruitment by Allen Dulles to the bitter day of his expulsion from the agency.

However, to call Spytime a fictionalized biography would be slightly misleading. Much of the second half is more like a conventional spy story, describing the adventures (if "adventures" is not too upbeat a word) of Angleton's young American protege Tony Crespi, on his first assignment as a deep-cover agent in Beirut, where he has been told to keep an eye on Kim Philby. Philby was once a colleague whom Angleton trusted, but now he is known, or suspected, to have been the most important in a whole bunch of traitors at the heart of Britain's Secret Intelligence Service.

The narrative technique consists of short datelined chapters lacing together Angle ton's personal story with all the intelligence-related dramas of the period; these begin with Mussolini's capture by Communist partisans in 1945, at which Angleton was allegedly present, and range through Khrushchev's revelatory speech about Stalin, the building of the Berlin Wall, the Bay of Pigs disaster, the Cuban missile crisis, and the Viet nam War, accompanied by the re curring enigma of doubtful defectors and double agents. Most of this background information has gradually emerged into the public domain, but Buckley supplements it with material from his own rich experience and wide acquaintance.

Therein lies the major difficulty of this peculiar genre. The reader is never quite sure of the line dividing ascertained fact from informed imagination: He cannot know which details have been un earthed from contemporary memoirs and which have been added for verisimilitude by the novelist. One is inevitably alert for implausibilities. One wonders: Did Jack and Bobby Kennedy really talk to each other in quite this style? Is there any foundation for the brief sexual episode involving Angleton? Can the directors of the CIA actually have discussed his removal in such a curt, cold-blooded way?

On the other hand, plausibility is not the same thing as truth; the truth must sometimes be toned down to render it plausible; a well- constructed falsehood is, almost by definition, easier to swallow. Who would readily have believed that the head of the Soviet section in the British intelligence service was himself as Soviet spy, a man so well regarded by British and allied colleagues that he might (stretching credulity still further) quite possibly have gone on to become head of the whole service? And yet it was so. Conversely, there are still people who believe that a man, now dead, who did become head of the service was indeed a spy; which is probably not so. Others within the intelligence community believed that Britain's prime minister, Harold Wilson, was himself at least a Soviet agent of influence. This is almost certainly not true, although some of his friends and associates may well have been, and he himself constantly feared that he was being plotted against by secret forces. Angleton saw no reason to believe that American politics and the CIA were immune from such sinister penetration. The British spy ring-Philby, Burgess, Maclean, An thony Blunt-had proved real. There was rumored to be a Fifth Man. The Fifth Man could be American.

If working for half a lifetime in what has justly been called a wilderness of mirrors, mapping it, using it, being deceived by it, finally pushed Angleton over the edge of rationality, who should be surprised? He saw conspiracies everywhere because in his world there were conspiracies everywhere. But perhaps not absolutely everywhere. Then again, who knows? This ultimate kernel of doubt Buckley leaves unsettled, as in a book where the characters are real and the narrative is not wholly fictitious, he was bound to do.

Taken just as a thriller, Spytime works well and moves fast: But there is always another dimension. Only the most imperceptive reader will not feel that Buckley is leading him down these mirrored paths of recent history for a purpose, to make him think about the nature of loyalty, about the subtleties of deception, about the extent of the Cold War, about who was right and who was wrong and how hard it can be to tell the difference.