THE GREATEST single difference between the actual world of espionage and that portrayed by most spy novelists is this: Real spooks, like the rest of us, often make mistakes and do not always know everything. Nevertheless, there is a persistent strain in the literature, taken to the extreme in Robert Ludlum's new book, that makes secret agents into all-powerful, omniscient beings whose successes are so predictable as to be monotonous -- particularly when their adventures are stretched out, as they are here, over 600 pages.

The protagonists of The Matarese Circle are the world's two greatest covert operators, an American and a Russian, who agree to work together, although they hate each other, for the good of humanity. The American never makes a false move, goes off on a wrong tangent, or fails to spot the most obscure clue. The KGB man is only slightly more fallible, but when he slips up, the American comes to the rescue.

Novelists are not photographers. with any particular obligation to recreate a slice of life. Yet, Ludlum has chosen to write a political thriller that uses the world as it supposedly is for its backdrop. This type of book works well when its plot flows naturally and realistically out of familiar circumstances, as was the case in Paul Erdman's Crash of '79 .

Ludlum not only gets wrong numerous small details (a setting on Nebraska Avenue NW, foreign service ranks, etc.), but he weaves together a story that is so farfetched as to give conspiracy theories a bad name. Taking that old chestnut of power-hungry Crusaders forming themselves into the Knights of Malta, Ludlum updates the idea and makes Malta the home base for the plotters. The action starts in 1911 when a crazed aristocrat named Guillaume de Matarese convokes a cabal aimed at world domination.

A frustrated seeker after power and riches, Matarese enlists similarly minded men from the United States, Russia, England, and Italy and convinces them that the best way to undermine the system of global order is to make available to the ruling class a corps of deniable assassins -- the Matarese Circle. He reasons that having available such a useful tool will lead world leaders into an orgy of destruction which, in turn will give the Matarese clique tremendous leverage over international politics.

Guillaume de Matarese arranges for his own death shortly after he puts the plot together, but his followers carry on. Their employees/assassins, identifiable by the circular bluish tatoo on their chests, succeed in killing the Archduke Francis Ferdinand at Sarajevo, Franklin Roosevelt (the stroke was a cover story concoctoed by "financial interests" unhappy with his policy toward the Soviets), Joseph Stalin, and John Kennedy.

Moving with the times, the latest generation of Matarese is funding the entire international terrorist movement. Matarese dupes include the Red Brigades in Italy, the Baader-Meinhof gang, the PLO, and America's own Weathermen, Minutemen, Ku Klux Klan and Jewish Defense League.

The Matarese are everywhere, inside governments and multinational corporations. Their adherents include the American Secretary of State, the chairman of the Joint Chiefs of Staff, the Soviet Ambassador, 12 percent of the German Bundestag, and 31 percent of the Japanese Diet. In fact, they are on the point of seeing one of their own elected president of the United States -- the charismatic senator from Massachusetts, to be exact. (Without question, the scope of this plot dwarfs anything ever attributed to the Council on Foreign Relations or the Elders of Zion.) Luckily for us non-Matarese, the two secret agents find out what is happening and slice through the conspiracy like hot knives in butter.

Although the heroes claim they only kill out of necessity, good reasons seem to crop up every few pages, and the bodies pile up at a rate that would have kept the Church Committee busy for years.

Obviously there is a market for this sort of conspiracy and mindless violence, as proved by the fact that Ludlum always hits high on the best-seller lists. The Matarese Circle will probably secure itself a niche there too.