What makes puzzles-jigsaws, mazes, riddles, sudokus-so satisfying? Be it the formation of new cerebral pathways, their close link to insight and humor, or their community-building properties, they're among the fundamental elements that make us human. Convinced that puzzles have made him a better person, A.J. Jacobs-four-time New York Times bestselling author, master of immersion journalism, and nightly crossworder-set out to determine their myriad...