BOOK REVIEW : A High Standard for Low-Brow Humor : THE LIAR: A Novel <i> By Stephen Fry</i> ; Soho Press $22, 277 pages

Stephen Fry, actor and now novelist, has described the brilliant lead character in his book “The Liar” as someone who “dislikes telling the truth.”

That appraisal is a little off the mark, however, for prep-school provocateur Adrian Healey seems more allergic to the truth than anything else: his constant, extravagant lying is an integral part of his personality, a knee-jerk second nature, a way for Healey to distance himself from the world while mocking it at the same time.

Donald Trefusis, an eccentric professor at Cambridge University and Healey’s tutor, is on the money when he tells his charge, “You try to persuade others, never yourself. You recognize patterns, but you rearrange them where you should analyze them. In short, you do not think.”

As the preceding passage indicates, “The Liar” has serious moments. But Fry, best known in this country for his roles in the PBS series “Jeeves and Woosters” and the movie “Peter’s Friends,” is above all an entertainer, meaning that sober thoughts enter this novel only through the back door: Trefusis may call Healey “a fraud, a charlatan and a shyster,” but immediately turns the criticism around by adding that the boy is nonetheless “My favorite kind of person.”

Trefusis isn’t kidding, either: an eccentric character originally created by Fry for BBC radio, Trefusis believes Healey’s transparent amorality will make him a fine accomplice on the James Bond-like undercover mission on which the professor has recently embarked.

Given that most of “The Liar” takes place within the English educational system, and that Fry’s language is blushingly scabrous, one keeps expecting Healey’s life to be characterized by the author as little but sodomy and skulduggery.

Sodomy is more talked about than realized in the novel, despite the fact that Healey is flamboyantly homosexual and becomes, for a time, a male prostitute in Piccadilly. But make no mistake: “The Liar” is deliberately and exuberantly offensive, Fry reveling in the low-class jokes, stunts and incidents around which Healey has organized his life.

There’s his ability to live by “pastiche and pretense,” having “read and absorbed more than he could understand”; his fabrication at school of a “lost” pornographic novel by Charles Dickens, instantly snapped up for television; his affair with an actor and subsequent arrest on drug charges; and most damningly of all, perhaps, his willingness to cheat at cricket. Healey is, in short, a campus star, the envy of his peers and a pike in the side of every authority he encounters.

Fry has written for radio and the stage (he was a script doctor for “Me and My Girl”) and has even been a newspaper columnist (for London’s the Listener), so it’s no surprise that “The Liar” is a very professional piece of work.

It is a surprise, however, to learn that the novel is semi-autobiographical, Fry not only resembling Healey in that he was also considered “too bright for education”--so said one of Fry’s teachers--but also having spent a few months in jail (for credit card fraud, in Fry’s case, not drug possession).

Fry was never a boy prostitute, though: he claims, in fact, to be sex-averse, having been famously celibate for more than a decade. (Healey, who enjoys bed partners of both sexes, would no doubt be amused to hear that when “The Liar” was released in Britain in 1991, the Guardian quoted Oscar-winning actress and fellow Cambridge graduate Emma Thompson as saying of her long-time friend, “I’ve taken to walking downstairs nude just to frighten Fry. . . .It really is one of my favorite pastimes.”) But the most surprisingly thing about “The Liar,” ultimately, is how successfully Fry transforms the sophomoric into the sophisticated--a skill shared, not coincidentally, by both his protagonist and Fry’s comic forebears, Monty Python.

Moreover, although Fry has burdened “The Liar” with a complicated plot and a needlessly disjointed narrative, Healey’s inevitable comeuppance isn’t easily predicted. Yes, he does begin to question his native cynicism--but what Healey learns isn’t that cynicism can run too deep, but that the world is even more cunning than the most jaded college graduate can imagine.

“The Liar” is a novel of which any writer could be proud, and remarkable considering that writing, for Fry, is a second career.