You've probably never heard of Martin Gardner. But if you enjoy magic tricks, mathematical games and puzzles, the philosophy of science and the debunking of bad science, he might just be your hero.

To his fans, Martin Gardner, a 91-year-old widower, is revered as a genius; since 1993, six "Gathering for Gardner" conventions have been held in Atlanta. By invitation only, "G4G" brings together some 200 professional mathematicians, magicians and puzzle collectors. As Michael Dirda said in a review of one of Gardner's many essay collections, Are Universes Thicker than Blackberries? (Norton, 2003): "This Renaissance man of words and numbers remains as much a national treasure as ever."

Gardner has written or edited more than 70 books. Next month, W.W. Norton will publish his latest, The Annotated Hunting of the Snark: The Definitive Edition (Reviews, Aug. 21). This edition of Lewis Carroll's long nonsense poem is the companion volume to Gardner's The Annotated Alice: The Definitive Edition (Norton, 1999), which has sold 55,000 copies in hardcover. First published by Clarkson Potter in 1960, the original Annotated Alice was an innovation in its day. "Several houses rejected it," says Gardner. "One dismissed it with the comment: 'Annotating a children's book—that's hilarious!' "

Gardner lives in Norman, Okla., at an assisted living center. A reproduction of a print by M.C. Escher, the Dutch artist of curious and sometimes "impossible" geometric spaces, hangs on the door to his room but inside, on the wall above his bed, is an original Escher print, which Gardner bought for $60 before the artist became famous. The room also displays a couple of optical illusions: a toy pig that hovers in mid-air above a covered dish with a hole in the top (the pig looks solid, but as soon as you raise the lid, it disappears) and a portrait of Gardner made up entirely of dominoes—white spots on black—that's recognizable only from a distance.

While polite and reserved, with features that betray little emotion, Gardner is a master of deadpan wit, an aspect of his work his fans relish as much as his plain, factual style or his ability to make complicated science understandable. A lover of Sherlock Holmes, the Oz books and other literary classics, he doesn't care for poetry that lacks rhyme or meter. And four-letter words offend him, though he has a taste for the risqué, as shown by a certain optical trick he likes to perform that involves a spoon and the human hand.

Gardner's son Jim, a professor at the University of Oklahoma who often drops by, has bought his father a computer, but so far Gardner has used it only to play chess. "I set it at the easiest level, and it still beats me," he admits. Also, he's "scared to death of the Internet," afraid that "I'll get hooked and end up wasting my time."

Some of his time Gardner puts into negotiating his own contracts. He has used a literary agent only once—on his first book, In the Name of Science (Putnam, 1952), which debunked UFOs, orgone therapy and other pseudoscientific fads. A flop in hardcover, it was picked up by Dover and reissued in revised form under the title Fads and Fallacies in the Name of Science (1957), and has been in print ever since. While Dover usually offers its authors a flat fee, the publisher pays Gardner a modest royalty on Fads and Fallacies.

Over the decades, Gardner has had many publishers: Random House, Simon & Schuster, Scribner, Knopf, Morrow, St. Martin's, W.H. Freeman and Sterling. He has done 18 titles with Prometheus Books, a house known for titles that take a skeptical approach toward religion and extraordinary claims of the paranormal. Gardner explains his skepticism with a quip: "I'm a Libra, and it's been astrologically proven that Libras are skeptical of astrology."

He didn't always take this attitude. Born Oct. 21, 1914, in Tulsa, Okla., Gardner became a Christian fundamentalist in his teens under the influence of a Sunday school teacher. He lost his faith at the University of Chicago, where he majored in philosophy and studied under logical positivist Rudolf Carnap. Since then, he has been a "philosophical theist." Adam Gopnik, in his new introduction to TheAnnotated Snark, points to the appeal of Gardner's worldview: "Gardner speaks for all of us who love the imagination of the marvelous and gag on the puerilities of dogmatic religious belief."

Gardner's favorite among his own books is The Whys of a Philosophical Scrivener (Morrow, 1983) because it sums up his basic beliefs. A pseudonymous review in the New York Review of Books crankily picked apart the book's arguments and then, the last sentence revealed that the review's author was Gardner himself. "I didn't want to give it away, but my editor, Robert Silvers, insisted," he says.

Gardner's philosophy is also explicit in his autobiographical novel, The Flight of Peter Fromm (William Kaufmann, 1973). John Updike was so impressed that he wrote Gardner a letter, excerpts of which were used on the jacket of the Prometheus reissue ("a wonderful book.... I liked not only its abundant facticity but the surprising and persuasive surreal touches"). Vladimir Nabokov was another Gardner admirer. According to a note in Gardner's book on symmetry, The New Ambidextrous Universe (Freeman, 1990), an earlier edition of The Ambidextrous Universe was an influence on Nabokov's novel Ada.

The New Ambidextrous Universe is an example of how Gardner has challenged mainstream as well as fringe science. In it, he questioned the fashionable super-string theory, which strives to unite gravity and the other basic forces in nature. Sixteen years later, the New York Times Book Review (Sept. 17, 2006) reviewed two books that attack super-string theory.

As a critic of fuzzy thinking in science and religion (for years Gardner had a column called "Notes of a Fringe Watcher"—originally "Notes of a Psi Watcher"—in the magazine the Skeptical Inquirer), he has made his share of enemies stretching back to the 1950s, when New York—area talk-show host Long John Knebel, offended by Fads and Fallacies, used to regularly denounce Gardner as a liar on his radio show. "It was a great boost to sales," says Gardner.

William F. Buckley Jr. took umbrage at a review of his book Nearer, My God that Gardner wrote for the Los Angeles Times. Buckley's tart response to the criticism of his religious beliefs and Gardner's rebuttal can be found in Gardner's essay collection From the Wandering Jew to William F. Buckley Jr.(Prometheus, 2000). "I like to challenge people in print," says Gardner, "but not argue in person."

Unwavering in his convictions, Gardner claims that he's never been wrong about any of the people whose beliefs he's attacked. "In fact," he says, "I was too easy on J.B. Rhine, the parapsychologist, in Fads and Fallacies. I later learned he was much more of a crank than I realized." And despite his age, he's not about to embrace the consolations of religion. "A Protestant minister recently asked me if there was any hope of my becoming a Christian before I died," he says. "My answer was no."

Gardner's focus remains on the earthly task of writing, these days mostly reviews of math and magic books. He regrets that it's a while since he's been asked to review for the New York Review of Books. But he's putting together a new collection of essays on science and literature for Prometheus, The Jinn from Hyperspace, and there are books he has yet to find a publisher for, including a collection of critical essays on G.K. Chesterton. "I'm probably the only non-Catholic who's a Chesterton fan," he says. It's clear that Martin Gardner has enough to keep him busy for a long time.