BOOK REVIEW / FICTION : A Spy World Where Brains Count and Good Guys Win : SLEEPER SPY <i> by William Safire</i> ; Random House $24, 480 pages

Anyone who earns his living by expressing acerbic opinions on everything from presidential politics to English usage makes a fat target when he sits down to write a thriller, a genre in which a good yarn counts more than a clever turn of phrase.

But William Safire, conservative pundit and self-appointed guardian of good grammar, acquits himself well enough in his third novel, “Sleeper Spy,” a smartly done spy story with enough surprises to set it apart from the ordinary run of espionage fiction.

What’s at stake in “Sleeper Spy” is not honor or principle, top-secret technology or geopolitical strategy. Rather, Safire sets up an elaborate plot in which the key element is one big pot of money, which he calls “by far the most reliable motivation” when it comes to international espionage.

At the heart of Safire’s novel is a so-called sleeper, a Soviet operative who was planted in the United States by the KGB as a young man and then activated by his spymasters, who gave him $3 billion in gold and instructions to invest the money using insider information provided to him by their espionage apparatus.

Just about everybody in “Sleeper Spy” is looking for the nameless and faceless man with the money. The ostensibly “reformist” government of Russia, which desperately needs the sleeper’s fortune in hard currency, has set its own ragged band of spies on his trail, and so has the CIA. And a cabal of Russian “gangstercrats,” emboldened by the fall of the Soviet regime, want the money for their own malign purposes.

“The house is burning,” goes an old Russian saying invoked by the sleeper’s control agent, “and the clock is ticking.”

But the hero of Safire’s book is an unlikely character named Irving Fein, a once “legendary” but now down-at-heel investigative reporter who sees the story of the sleeper as his “meal ticket,” a chance to re-establish himself in a media Establishment that has been corrupted by pretty faces and light news.

“If the wrongos in Russia glom onto the fortune, they could finance the ultranationalists, build more bridges to the new mafiya,” says Fein to his literary agent, hoping to snag a book contract and a big advance. “A return to imperialism, Cold War Three, a new arms race, huge American defense budgets--you get some idea of it?”

Thus begins an espionage chess game of classic moves and countermoves--but Safire is too clever to content himself with simply moving his pieces around the board. No, he populates his novels with characters who are also caricatures, and he indulges himself in asides that are virtually in-jokes for conservative revisionists.

Fein’s agent, nicknamed Ace, is a stand-in for the late Irving (Swifty) Lazar, which allows the author to engage in a lot of prattle about book deals. Safire styles the head of the CIA as “the first acknowledged homosexual to be appointed to the post, and the first woman.” He suggests that Lee Harvey Oswald’s “handlers” in the KGB were executed to shut them up; he shows us the torture cell in KGB headquarters “where Raoul Wallenberg was executed.”

Then, too, Safire sets up a love interest for his gruff middle-aged reporter--a young, beautiful, and ambitious TV news personality named Viveca Farr, who hopes to plump up her journalistic credentials by teaming with Fein on a book about the sleeper.

“He would call it ‘virgule matching’--novice / old-timer, female / male, face / byline, crisp / sloppy,” Ace muses, “a form of casting almost as natural as Beauty / Beast.”

Now and then, Safire feels obliged to liven up the book with a bombing, a hijacking, even a striptease by a Latvian journalist with the obligatory “full and firm” breasts that are invariably bestowed upon women in spy novels.

But the formulaic moments are somehow halfhearted. “Sleeper Spy” crackles with wit and savvy--the author enjoys himself most when he gives us the world according to William Safire, a world beset with plots and conspiracies, a world in which brains count and the good guys (and gals) win.