What is your favorite book? What are you reading right now? Do your answers to those questions tell us anything meaningful about who you are as a person? Or is the book in your hand just something to pass the time, signifying nothing?

Sometimes it's tempting to think that a person's favorite book is the secret to unlocking his character. That's what makes Who Reads What — a directory of celebrities' favorite books assembled over a twenty-year period by Glenna Nowell of the tiny Gardiner (Maine) Public Library — so immensely fascinating. Sometimes the books seem to confirm exactly what we think we already know about their readers. We see that John McCain's favorite book is Hemingway's For Whom The Bell Tolls, a choice that rings perfectly true to the senator's lifelong adherence to stoicism and principle. Bo Jackson's choice of another Hemingway classic, The Old Man and the Sea, may at first surprise, but only because we're not used to thinking of star athletes as literary types; Jackson's determination to overcome his own degenerating hip in a futile effort to prolong his career in the early 1990s could have come straight out of a Hemingway story. It makes perfect sense that consumer-safety advocate and perennial presidential candidate Ralph Nader would find inspiration in Ida Tarbell's 100-year-old muckraking expose, The Standard Oil Company. And we get a strong hint of both Bill Clinton's energy and his indiscipline—his greatest strength and weakness as a politician—in his inability to choose just one favorite book; his five faves range all the way from James Fennimore Cooper to Gabriel Garcia Marquez.

Then there are the surprises. Nelson Mandela may have more gravitas than any other living human, and we know that he spent the many years of his apartheid-era imprisonment reading voraciously; we can thus buy completely that his favorite book is War and Peace. But Keira Knightley, who named the same Tolstoy classic as her favorite? Didn't see that coming. Kenneth Branagh, who has made his living reinventing Shakespeare for the stage and the screen, chose as his favorite book ever not something from the Bard but rather Charles Dickens's David Copperfield. (Less surprising: the same book was chosen by the magician who calls himself… David Copperfield.) Shakespeare was the choice of Supreme Court Justice John Paul Stevens, who loves Hamlet. But Stevens insisted that the play's author was "Edward de Vere, Seventeenth Earl of Oxford, writing under the nom de plume William Shakespeare." Who knew we had a conspiracy theorist on the high court? Should it raise an eyebrow that one of Bill Gate’s favorite books is the social-disaffection manifesto Catcher In The Rye, and that Gates says he can "quote large portions of it from memory"? Is it weird that Natalie Portman's favorite book is Lolita? Who's to say? Those are both great books, and if they're not necessarily the titles we would have expected, we can certainly see the appeal.

But then there are those times when the book and its reader just don't seem to fit together at all. In 2006, the White House conspicuously leaked the news that President George W. Bush was reading Albert Camus's The Stranger while on vacation. Say what? It was hard to imagine the famously down-to-earth president capping off a long day of clearing brush on his Texas ranch by settling down to a quiet evening of French existentialism— particularly at a time when all things French were being ridiculed by American conservatives. ("Freedom fries", anyone?) And the book's plot, centering on the cold-blooded murder of a random Arab man by an unrepentant westerner, could only provoke further head-scratching at a moment when Arab-American relations were already deeply strained by the War on Terror. Bush and Camus? What did it all mean? Bush press secretary Tony Snow's official announcement that the president "found it an interesting book and a quick read" didn't really answer the question; sadly, in all likelihood, not even the Freedom of Information Act will be able to help us solve the mystery and we'll never really know just what drew the president to dabble in existentialism. But it would sure be fun to know.