The Boston Globe's David Mehegan spotlights what may well be the most surprising bestseller this year: Dan Klein & Tom Cathcart's PLATO AND A PLATYPUS WALK INTO A BAR: UNDERSTANDING PHILOSOPHY THROUGH JOKES. Released in the spring, the 200-page book jumped onto the New York Times bestseller list and stayed for five weeks; it's still no. 32 on the 35-title online list (the printed list has 15 titles). The book's career so far demonstrates at least one point: Writers shouldn't give up too soon on a book they believe in.

Crammed with 143 jokes and an occasional cartoon, PLATO AND A PLATYPUS is a 10-chapter course on the classic categories of philosophy, written in a Marxist style (Groucho's), paced by the frequent appearance of Dmitri and Tasso, a comic two-man Greek chorus. The chapter titles -- "Metaphysics," "Logic," "Epistemology," "Ethics," "Existentialism," and "Philosophy of Language" -- are serious, but the content that follows is anything but. It helps that the two men, friends for 50 years, have differing perspectives: Klein is a former TV writer while Cathcart eventually became chief operating officer of Mercy Hospital in Portland, Maine.

The idea came about after a 2004 vacation, and after less-than-enthusiasm from Klein's longtime agent they approached Julia Lord, who "loved it" and proceeded to collect almost 3 dozen rejections before Abrams picked it up. Everyone is surprised by the book's success, but not enough to stop Klein and Cathcart from concocting a sequel. ARISTOTLE AND AN AARDVARK GO TO WASHINGTON: UNDERSTANDING POLITICAL DOUBLESPEAK THROUGH PHILOSOPHY AND JOKES is due out next winter -- just in time for the election season, when we can all use a laugh.