As a young scientist at Los Alamos during the development of the A-bomb, Richard Feynman delighted in exposing security lapses by picking the locks on safes and filing cabinets that contained top secret information, leaving behind notes signed, "Same guy." But there were even earlier warning signals that the Nobel prizewinning physicist and California Institute of Technology professor had, as one friend says, "a mind that works differently from other people's." As a toddler in Far Rockaway, N.Y., his father, Mel, a uniform salesman, read him excerpts from the Encyclopaedia Britannica. And as a teenager he read advanced calculus for pleasure.

Now Feynman, 67 and considered one of the world's top theoretical physicists, can claim another achievement: his deliciously amusing autobiography, Surely You're Joking, Mr. Feynman! (W. Norton, $16.95). Co-authored by Ralph Leighton, a math teacher who started taping conversations with his friend Feynman seven years ago, the book spent 14 weeks on the New York Times best-seller list, a surprise to practically everybody—including the author. "I had no purpose in doing the book other than to amuse my friends," says Feynman.

A picturesque, unscientific collection of anecdotes, including instructions for picking up a woman in a bar, Surely You're Joking has earned Feynman $56,000 so far and has elicited reaction from some unexpected quarters. "I got a call from a topless dancer," he says, "who claims we had a mutual acquaintance 15 years ago."

At times brash, moody and argumentative, Feynman is never without a mischievous sense of humor. He has refused to promote the book on tour, but cheerfully reads aloud a headline from one of the few interviews he granted: "Nobel Prizewinner Says: 'Most Experts Are Full of Hot Air.' "

If that's true, then some might suggest that Feynman has sprung a leak. During a 1951 lecture tour in Brazil, he played frigideira (a toy frying pan) for a samba band. He draws sketches of nudes (he was once commissioned by the owner of a massage parlor) and appears as an Indian mystic in a painting—one of a series of famous Caltech scientists—by artist Sylvia Posner.

Feynman even had to be talked into showing up to accept his Nobel prize in 1965 because he dislikes pomp and royalty. He is still loath to spell out, in layman's terms, why he won. "Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize." He shared the $5500 prize with Japan's Shinichiro Tomonaga and Julian Schwinger, then of Harvard, for work in quantum electrodynamics. Gweneth Howarth, Feynman's British-born third wife of 25 years, concedes, "He can be very boorish. Sometimes he goes too far, and I tell him to shut up." (His first wife died in 1946; a second marriage ended in divorce.)

On the trip home from the Nobel ceremonies in Stockholm, Feynman stopped at his high school in Far Rockaway, where he looked up his grades and IQ score. "My grades were not as good as I remembered, and my IQ was 124 or 126, considered just above average," he says. Reports Gweneth: "He was delighted. He said to win a Nobel prize was no big deal, but to win it with an IQ of 124, now that was something."

An inquisitive child who viewed science as a puzzle, Feynman was repairing radios in the neighborhood at age 12. His younger sister, Joan, also became a physicist and is employed by Pasadena's Jet Propulsion Laboratory. He graduated from the Massachusetts Institute of Technology in 1939 and earned a Ph.D. from Princeton in 1942. Feynman claims he missed military duty in World War II because the Army ruled him mentally unfit. When an Army psychiatrist asked how much he valued his life, he responded with an arbitrary "64." While at Princeton he went to work—with some hesitancy—on the Manhattan Project, where he brushed elbows with geniuses like Edward Teller and J. Robert Oppenheimer, who were developing the atomic bomb. He figured that if the U.S. didn't develop the bomb quickly, the Nazis would. Still, after the A-bomb was dropped on Hiroshima and Nagasaki, he slipped into occasional dark moods and would "sit in a New York restaurant and figure how many miles around would be destroyed if a bomb hit."

He met Gweneth in Switzerland in the '50s. She was drawn not to his work but to his "great sense of fun," she says. They have one son, Carl, 23, a computer scientist in Cambridge, Mass., and a daughter, Michelle, 16.

Feynman feels he is currently going through a bit of a slump because he has not had a "first-rate breakthrough" in eight years. He's not worried, though: "I've had these times before, followed by moments of great discovery." He is investigating "the forces that hold the nucleus together, looking for the patterns behind the particles." He's stumped, he says, "and it's driving me crazy."

But Feynman has never been one to be outdone by science. "I'm comfortable with uncertainties," he declares. "I don't go to psychologists because I don't think they have any more answers than I do." And surely Mr. Feynman isn't joking.