First, think of a beginner's guide to philosophy, written by a schoolteacher for teens and young adults. Next, imagine a fantasy novel -- something like a modern-day version of Through the Looking Glass. Meld these disparate genres, and what do you get? Well, what you get is an improbable international best seller.
To the amazement of its Norwegian author, Jostein Gaarder, 42, Sophie's World, subtitled A Novel About the History of Philosophy, has become a runaway hit practically everywhere it has appeared. In the author's homeland, it has been on the best-seller lists for nearly four years. The novel has been...