By William Boyd

Knopf. 498 pp. $24.95

One of the pleasures offered by William Boyd's new novel, Any Human Heart -- and its pleasures are countless -- is perhaps the simplest one a reader can know: following a character through his or her life. For that is humbly what this novel, written in the form of an "intimate journal," does: It details the life of one Logan Mountstuart, who has what in retrospect he comes to see as the great good fortune of living "in every decade of this long benighted [20th] century."

Logan is born in 1906. It seems to me a very fortuitous time to be born, and the novel seems intent on illustrating that point, but Logan himself is not sure. Early on in his lengthy, eventful life, he wishes he had been born "two decades earlier . . . this was the literary life I should have lived." And at the very end of his life, confronted by the evidence of the sexual revolution, he wonders if perhaps he should have been born at the end, rather than the beginning, of the century. But he exits the book, and his life, wondering if "any of you will live as well as I have done."

Probably not. Logan is born in Montevideo, Uruguay, to a British father and a Uruguayan mother, and he spends his youth in that "Switzerland of South America." His father (the general manager of a frozen meat company) is decent, moral and dies an early death; Logan's mother is beautiful, vivacious and impractical, and Logan appears to inherit the best qualities of both. His journals begin in 1923, as the family moves to Birmingham, and he is a student at Abbeyhurst College, "an eminent boys' boarding school, though not quite of the first rank." He goes on to Jesus College, Oxford, where he reads history, acquaints himself with the literary vanguard and begins writing his first book, a biography of Shelley. (A later novel and a book of literary criticism complete his published oeuvre.) He also embarks on his sexual life while at Oxford, having a clandestine affair with his best friend's lower-class lover.

Emerging from Oxford (with a disappointing third-class degree), Logan shuttles between Paris and London in the '20s, establishing a long-term and formative relationship with a middle-aged Russian prostitute in Paris while pursuing his first real love, an intellectual bohemian named Land Fothergill, in London. When both women disappear from his life, he makes the mistake of marrying Lady Laeticia (Lottie) Edgefield, an insipid woman whose features "conspire to keep her the plain side of fairly pretty."

He begins to dread his marriage on his honeymoon, as well he should: It isn't long before he's ensconced in a country manor house with a wife he can't stand and a baby son from whom he feels at best estranged and at worst repulsed. Logan escapes from this me{acute}nage by taking an apartment in London, spending the weekdays there and beginning an affair with an appealing younger woman named Freya.

Thus begins the happiest period of Logan's life. Upon discovering his infidelity, Lottie divorces him, and he quickly marries Freya. They have a daughter, Stella, but their domestic idyll is interrupted by the advent of World War II. Logan joins the Naval Intelligence Division and is posted first to Portugal and then to the Bahamas, to "keep an eye on" the exiled duke and duchess of Windsor. (Logan had earlier met the duke on a golf course in Biarritz -- one of his enduring talents is his Zelig-like ability to meet a 20th-century personage every time he turns around.) His failure to cooperate with the royal couple when they become involved with a nasty local murder prompts his swift removal from the "moron paradise" of the Bahamas. He spends the rest of the war as a prisoner in a lakeside villa in Switzerland, after parachuting into the country on a failed mission to entrap fleeing Nazis by impersonating a Uruguayan businessman.

His two years of solitary confinement wear upon his spirit, which is totally broken when he returns to London to devastating personal news. After a failed suicide attempt in postwar Paris, he spends the next decade running an art gallery in New York City, marrying again and befriending -- or alienating -- the entire cast of the New York City School of painters and poets. He even manages to dramatically re-encounter his former nemeses, the now-ghoulish duke and duchess. An unsavory combination of drunkenness and infidelity ruins Logan's new life in the new world, and he is forced to flee, briefly taking refuge as professor of English Literature at a Nigerian university before living out his twilight years in genteel poverty in rural France.

Logan's life might be preposterous -- in his sixties he joins up with a revolutionary terrorist group mainly because he is bored -- but it is certainly engaging, and Boyd clearly enjoys intertwining his charismatic hero's life with the cultural history of the century. At Oxford, Logan meets Evelyn Waugh, Henry Green and Anthony Powell, not to mention a country-house full of Bloomsberries. (An unsaintly and self-congratulatory Virginia Woolf -- a "silly" writer, in Logan's opinion -- reappears several times throughout the book, uttering breathtakingly racist or pretentious statements.) In Paris, Logan drinks with Picasso and dines with Hemingway, who accompanies him to the front lines of the Spanish Civil War. His cohorts in the Naval Intelligence Division are none other than Ian Fleming and William Plomer, and it's not everyone who spent his war drinking gin and playing golf with Wallis and Bertie. And Logan doesn't seem to be in New York City more than 15 minutes before he's arguing with Frank O'Hara in the Cedar Tavern.

What does Logan's life say about life -- or at least the artistic life -- in the 20th century? It's worth noting that he makes his fortune through the buying and selling of paintings, not via his writing: Only one of his books, a schmaltzy-sounding novel based on his romantic infatuation with the Russian prostitute, proves profitable, and after the war he is unable to write or publish. Writing, as a viable form of the artist's life, seems, in other words, to expire as the century wanes. "It's all changed," Logan's exhausted literary agent tells him upon retiring in 1969. "All they're interested in is sales and advances." He meets fewer celebrities in his last three decades, and the world of art seems to lose much of its glistening importnance. Perhaps Logan's ability to be in the right place at the perfect time disappears, but it's just as likely that as the world decentralizes, such singular places cease to exist.

But fortunately Logan is a fully rounded character, not a mere Zeitgeist device. Near the end of the book his stepdaughter, a sensible American teenager named Gail, lists her stepfather's virtues: He's "English, works in the art world, knows all the groovy artists, has lived all over the place, has written novels, has been in prison." Logan is flattered by this list -- "even I begin to think what a tremendous fellow I am" -- but the reader realizes that all these attributes are rather circumstantial and hollow. None of them actually speaks to the kind of man Logan is.

That is why the ending of this supremely entertaining book is so moving, for Logan Mountstuart, who is born male, rich, white, handsome and arrogant at the beginning of the century, dies a modest, kind and wise man. In his old age he selflessly nurses a former lover through her final, gin-soaked illness, and he bravely strives to protect a French friend from reactionary vandals. His shrinking purse, meanwhile, has reduced him to eating dog food ("very tasty Bowser rabbit stew turned out to be, with the liberal addition of tomato ketchup and a jolt of Worcestershire sauce"). This from a man who dined regularly at the Ritz. Logan Mountstuart, as portrayed by Boyd, is convincingly, and movingly, humbled by the century that informs his life. *

Peter Cameron is the author of four novels, including "Andorra" and "The City of Your Final Destination."