Yet this month Vonnegut will publish ““Timequake,’’ his 19th and–if you believe him–last book. Though he talks matter-of-factly about old age and death, he remains active: lecturing, painting, unrepentantly smoking, appearing in ads for the Discover Card and raising a 13-year-old daughter with his wife, the photographer Jill Krementz. And ““Timequake,’’ a fictional/autobiographical mElange that resurrects his famous alter ego, the science-fiction writer Kilgore Trout, happens to be his funniest book since ““Breakfast of Champions’’ in 1973. Still, Vonnegut protests. ““Human beings didn’t use to live as long as I have. I’m old. But I had to try another book. It is usually regarded as gallant when somebody tries against the odds.''

Vonnegut is notoriously skilled in this business of lowering reader expectations. In the introduction to his 1969 World War II masterpiece, ““Slaughterhouse Five,’’ he called the book ““a failure.’’ The book’s structure, jumping back and forth through time, cleverly reflected the cultural vicissitudes of the decade, and took the author from science-fiction shelves to literary prominence alongside other authors writing about the war, like Norman Mailer and Joseph Heller. His recent books are less imaginative, and proudly out of touch with today’s technological society. But his lowbrow humor and regular autobiographical musings about his life and upbringing continue to capture successive generations of fans, many of them students who get hooked on Vonnegut in high school. This is why Vonnegut chat groups and Web pages are popular on the Internet, and why, unlike many of his peers’, all of his books are still in print. ““After I die,’’ he says, ““I’ll still be talking my head off.''

So now we add ““Timequake’’ to Vonnegut’s clamor. The book was intended as pure fiction, the story of a glitch in the space-time continuum that rewinds the universe from 2001 to 1991, making everybody relive the past decade exactly as they did the first time. It was scheduled for publication several years ago, until Vonnegut changed his mind and yanked it. ““If I didn’t understand it and like it, why would anybody else?’’ he says. Still, he owed the book to his publisher, Putnam, as the third of a three-book contract. So he set about gutting the work and combining its best parts with nostalgic ruminations, a few dirty jokes and an account of his tangle with the creative menopause of old age.

The book’s resulting choppiness will almost certainly befuddle Vonnegut’s new readers. But to the faithful, ““Timequake’’ offers one last satisfying romp. In the book’s fictional portions, Kilgore Trout, the forlorn hack writer who throws away his stories as soon as he finishes them, endures the decadelong rerun, then schemes to save New Yorkers immobilized by the sudden return of free will–what Vonnegut calls ““post-timequake apathy.’’ He writes, ““In real life, as during a rerun following a timequake, people don’t change, don’t learn anything from their mistakes, and don’t apologize.’’ Interspersed with that story, Vonnegut serves up some characteristic vitriol on, among other things, mindless television, education from computers instead of books (““please, please, please wait just a minute!’’ he writes) and what he calls ““the death of American eloquence.’’ There are nuggets of Vonnegutian wisdom throughout. Sainthood is defined as ““a person who behaves decently in an indecent society.’’ The number of people with lives worth living is calculated at 17 percent. Hitler’s last words are hypothesized. (““I never asked to be born in the first place.’')

There’s also a palpable sadness that winds through ““Timequake,’’ as the author tells the real story of his older brother Bernard’s sickness and eventual death from cancer. Vonnegut’s ex-wife, his comrades from World War II and various writing friends are also poignantly remembered. ““I don’t have survivors’ syndrome from the second world war, but I sure do from the writing profession,’’ he says. He also mourns the business of writing. ““We are not needed anymore. There were books back when I started out that everybody would be talking about,’’ he says. ““Today the big one they are excited about is by Paula Barbieri.''

But then he laughs again, that deep, guttural chuckle. His wife thinks it’s all a bluff. ““I don’t believe for a moment that he’s giving up writing,’’ she says. For now, at least, Vonnegut is busy promoting his book, writing humorous commentary for a New York public radio station and developing a new love, painting. His silk screens, printed by the author on acetate and then colored by an artist in Kentucky, feature naked women, sad, old men and unmentionable body parts. It’s classic Vonnegut. And it’s more evidence that the little radio inside his head may still be working after all.