If you're a regular Savage Love reader—and if you're not a regular Savage Love reader, your last name is probably Santorum—you know that Dan Savage has called the book that Christopher Ryan coauthored with Cacilda Jethá, Sex at Dawn: The Prehistoric Origins of Modern Sexuality, "the single most important book about human sexuality since Alfred Kinsey unleashed Sexual Behavior in the Human Male on the American public in 1948." It's a study of the birth and creation of human sexuality, and its revelations about monogamy and group sex are guaranteed to rock your sexual world. (Elliott Bay Book Company, 1521 10th Ave, 624-6600, 7 pm, free)