BOOK REVIEW / NOVEL : Thriller Portends a Dark Political Future : SHELLEY’S HEART <i> by Charles McCarry</i> , Random House, $23, 567 pages

“Shelley’s Heart” is a smart and savvy political thriller set “at the dawn of the 21st Century,” which means that the terrain is familiar enough: Terrorism and assassination are commonplace, politics is tinged with paranoia, and the world is awash in a kind of apocalyptic dread.

“There was no such word as coincidence in his vocabulary,” writes author and journalist Charles McCarry about the key villain in his book, an unlikely but memorable fellow named Archimedes Hammett. “All unexplained events were the result of a conspiracy.”

A stolen presidential election is what sets “Shelley’s Heart” into motion, and we quickly find ourselves hurtling toward impeachment and perhaps even a coup d’etat. But political intrigue is only the stage upon which a still more ominous conspiracy is acted out.

“The Establishment . . . must be conquered camp by camp--first academia . . , then the news media, the churches, and the arts,” muses Hammett, “then, in the Year Z, the whole world.”

Indeed, the title of McCarry’s book alludes to an imagined cabal of high-minded but dark-willed intellectuals for whom the curious lore surrounding the death of Percy Bysshe Shelley becomes the motive as well as the mechanism of conspiracy. They seek to “do good by stealth” and thereby hasten “what Shelley called ‘the moral progress of politics,’ ” even if it means the ruthless murder of both human beings and American democracy.

Arrayed against the conspiracy, if sometimes unwittingly, is an unlikely alliance of politicians, journalists and attorneys, including an intrepid reporter named Macalaster and a pair of richly imagined American Presidents who, frankly, make our own real pols seem awfully sorry by comparison.

The incumbent President, “Frosty” Lockwood, is a Lincolnian figure--”outsize, noble, ugly”-- whose preferred form of exercise is wielding a pick and shovel alongside the White House groundskeepers. His apparent nemesis is a former President named Franklin Mallory, a curiously endearing reactionary and a cracked but idealistic entrepreneur who set up a vast embryo transplant service called “Morning After Clinics” as a way of discouraging abortions.

McCarry’s vision of the not-so-distant future of American politics is hardly the stuff of science fiction, but he does come up with some intriguing speculative touches in his description of life in the next century.

Deer are commonly seen in the streets, he writes, because of the successes of “the animal rights lobby” and the “environmental police.” The CIA has been folded in favor of a new intelligence agency “modeled on the Federal Reserve Board.” And the presidential ballot is crowded with culturally diverse candidates, including one who represents the Vegetarian Party.

Certain verities of the genre do not change, however. The terrorist who turns out to be a cat’s paw of the conspirators, for example, is purely a stock character, a “sheik who wanted to nuke all the Jews.” And I detected a certain animus--and a plainly anti-PC sense of humor--in the sometimes barbed and sometimes dismissive treatment of environmentalists, feminists and all characters who happen to be women.

Still, McCarry aspires to (and achieves) a certain elegance and stature in “Shelley’s Heart,” and--as he makes clear in an afterword--he worked hard to achieve technical and historical accuracy in the details of his storytelling. Indeed, the narrative is especially convincing when the author is describing what he knows best, the inner workings of inside-the-Beltway politics.

But what really distinguishes “Shelley’s Heart,” what makes the book such a hot read, is its zaniness rather than its scholarship. Rather like the best of Richard Condon’s novels, the experience of “Shelley’s Heart” is akin to waking up in someone else’s fever dream, an Alice-in-Wonderland world where even the wackiest stuff seems to make sense right up until the moment when the ax man’s blade falls.