In 1991, the Library of Congress surveyed more than 2,000 readers and crafted a list that it grandly called "25 books that have shaped readers' lives." The list included many of the usual suspects: The Bible, of course. "Don Quixote." "The Catcher in the Rye." But there at the bottom, lodged alphabetically between "War and Peace" and "The Wizard of Oz," was a business book -- the only such book on the list, and the only volume, fiction or nonfiction, whose title poses a question: "What Color Is Your Parachute?"

Richard Nelson Bolles, now 72, offered up that inscrutable question 30 years ago when he wrote the first edition of "What Color Is Your Parachute?: A Practical Manual for Job-Hunters and Career-Changers" (Ten Speed Press). It was one of the first job-hunting books on the market. It is still arguably the best. And it is indisputably the most popular, measured by its status as one of the best-selling books of all time: 288 weeks on the New York Times best-seller list, 6 million copies in print, between 15,000 and 20,000 copies sold every month.

But as the Library of Congress list suggests, the book's impact reverberates beyond bookstore cash registers. Like few other questions ("What's your sign?" and "Where's the beef?" come to mind) "What color is your parachute?" has become a comfortable part of the American vernacular.

What color is your parachute? Answer that riddle, and you've unlocked some fundamental secret about your work and your life.

Well, not quite, says Bolles.

"The question was just a joke," explains Bolles. "I had no idea that it would take on all this additional meaning." He first posed the question at a meeting in 1968. Somebody told him that several people in his organization were "bailing out." So to remind himself that he needed to discuss the topic, he scribbled "What color is your parachute?" on the blackboard. His colleagues chuckled. And that might have been the end of it -- another one-liner forgotten before the laughter subsided.

But as it turned out, Bolles himself was one of the bailers. As an ordained Episcopal priest, he was canon pastor of Grace Cathedral in San Francisco. But he lost his job in a budget crunch. He then landed an administrative position with the Episcopal Church, meeting with campus ministers at colleges across the country. He discovered that many of these ministers shared his predicament: Their jobs were in peril, and they had no idea what to do.

So Bolles did some research and wrote a 168-page guide to help the campus ministers he was supervising find jobs and change careers. Stuck for a title, he remembered his wacky question from two years earlier. He self-published the book in 1970. The first pressrun was 100 copies, which Bolles toted to a meeting in Philadelphia and distributed free of charge. Then something extraordinary began to happen. He started to get orders -- first for 1 or 2 copies, then for 40 or 50. Before long, orders were pouring in -- not from other ministers, but from such institutions as General Electric, the Pentagon, and UCLA.

By 1972, a small publisher in Berkeley, California produced "Parachute" commercially. "Of course, nobody knew what the title meant," Bolles says. "I'd go into bookstores and find it in sports, with books about parachuting." In 1974, a recession rocked the country, and "Parachute"'s sales soared and have remained sky-high ever since. For all of the changes in the world since the days of the Nixon administration, the book's core advice hasn't changed much. Finding a job is all about strategy. Choose the right strategy, and you can snare a good job even in bad times. Choose the wrong strategy, and even roads paved with gold will lead you nowhere.