Is thumb-sucking OK? And do we really need to wait 30 minutes to swim after eating? Jennings's first book described his one-of-a-kind Jeopardy! experience in Brainiac: Adventures in the Curious, Competitive, Compulsive World of Trivia Buffs, and he plotted his love of cartography in Maphead: Charting the Wide, Weird World of Geography Wonks in his second. The brainiac shares his top five gifts for trivia buffs this holiday season.