The Agony of Deceit : KGB; The Inside Story <i> By Christopher Andrew and Oleg Gordievsky (Harper Collins: $29.95; 776 pp.) </i>

After joining the KGB in 1962, Oleg Gordievsky grew disillusioned six years later when Soviet tanks clattered into Czechoslovakia, crushing the Prague Spring and its new brand of socialism that promised a human face.

In fact, Gordievsky grew so disillusioned that he offered his services to the British Secret Intelligence Services, which apparently accepted them with alacrity. While on the SIS payroll, or perhaps only in its thrall, Gordievsky continued to rise in his own spy service, eventually achieving the rank of KGB resident (head of station) in London.

In 1985, he was summoned back to Moscow for consultation. Suspecting that his treachery had been discovered, Gordievsky dissembled, stalled and eventually escaped back to London, leaving behind his wife and two small daughters. He has not seen them since.

In 1987, he teamed with Cambridge historian Christopher Andrew to write a history of the KGB. They would concentrate on how the Russian spy agencies have viewed the world as a huge conspiracy aimed directly at the U.S.S.R. The result is “KGB: The Inside Story,” a 776-page treatise that traces in often excruciating detail what Russian spies have done or tried to do from the time of Ivan the Terrible in 1565 to the present day.

As they follow the KGB through its permutations from its birth as the Cheka in 1917 to the various acronyms that followed--OGPU, NKVD, MGB, MVD and, finally, KGB--the historian and the ex-spy return again and again to the Soviet obsession with conspiracies, some of them real, many of them imaginary.

It also is a history of constant intrigue, rampant paranoia, numbing fear and, were it not for the wholesale butchery, it frequently reads like the inner workings of the Soviet Ministry of Agriculture gone slightly mad.

One of Gordievsky’s own and quite understandable obsessions is with Kim Philby, the late MI6 star and Soviet agent who almost became chief of Britain’s Secret Intelligence Service. Philby, of course, was the senior partner in the old-boy spy firm of Philby, MacLean, Burgess and Blunt.

The authors rather breathlessly reveal that there is yet a fifth member of the old-boy spy firm that the KGB is said to have begun calling “The Magnificent Five” after watching Steve McQueen, Yul Brynner et al in “The Magnificent Seven.” The firm’s fifth member is none other than John Cairncross--not exactly a household name in this country.

But the authors assure us that he was a most excellent Soviet spy. “In less than a decade after leaving Cambridge, he served successively in the Foreign Office, the Treasury, the private office of a government minister . . . and SIS.”

For those who out of curiosity or even perversity follow the careers of British double agents, both real and imaginary, John Cairncross is a familiar name. Back in 1984, Chapman Pincher, in his book “Too Secret Too Long,” devoted almost a dozen unflattering pages to Cairncross, charging him with most of the same treacherous deeds that Andrew and Gordievsky now accuse him of six years later. Cairncross, however, no longer denies anything, Pincher says. “He simply points out that he has never admitted having been a spy.”

For U.S. readers, Andrew and Gordievsky also offer a long list of Americans who have been charged, tried, convicted and even executed for having been Soviet agents. There are Alger Hiss and Whittaker Chambers, of course, although the authors note that their account of Chambers’ “career is based on Allen Weinstein’s ‘Perjury: The Hiss-Chambers Case,’ ” a book that many Hiss partisans still dispute.

The Rosenbergs, Ethel and Julius, are mentioned in a curiously sympathetic way. They “eloquently, even movingly, protested their innocence to the end. In April, they became the only Soviet spies in the west to be sentenced to death. . . . Both Julius and Ethel were dedicated, courageous Soviet agents, who believed that they could serve the future of their cause by denying their association with it.” There is no footnote to this assertion, but it seems likely to be a tribute of sorts from Gordievsky.

And then there is the curious case of Harry L. Hopkins, the man who was one of President Franklin D. Roosevelt’s closest advisers and sometimes even lived in the White House. According to Gordievsky, all the Soviet authorities he discussed Hopkins with agreed that “Hopkins had been an agent of major significance.” A Soviet agent, it should be noted.

Upon reflection, Gordievsky finally decided that “Hopkins had been an unconscious rather than a conscious agent.” In CIA parlance, that would be an unwitting rather than a witting agent. Unwitting agents often are none too bright, which is something no one ever accused Hopkins of being. However, after going through a rather tortuous analysis, the two authors finally agree that “In backing Stalin and the Soviet war effort, Hopkins acted from a determination to prevent a Nazi victory rather than from a secret commitment to the Communist cause.”

The Russians still think he was their agent. But then, so do many Republicans.

Perhaps too much of the book is devoted to intramural infighting in the Russian spy bureaucracies. But there is also a measure of titillating gossip about cyanide guns concealed in cigarette packs, the history of the famous umbrellas purchased in Washington and transformed into Bulgarian assassination weapons, and about how the KGB recruits its agents.

“KGB: The Inside Story” is essentially a long, long tale of deceit, treachery and politics by terrible means. In other words, it’s about espionage. It’s also a cautionary tale that in its final paragraph clearly states its warning:

“Like every major modern state, Russia needs both a domestic security service and a foreign intelligence agency. For it to possess an intelligence community worthy of its citizens’ respect, however, it will have to close down the KGB and start afresh.”

On second thought, it’s more of a dream than a warning.

BOOKMARK: For an excerpt from “KGB: The Inside Story,” see the Opinion section, Page 2.