Exploring what's been called the ``last acceptable prejudice,'' the authors strive to help readers understand individual differences, noting that some scientists prefer the term ``homosexualities'' to denote varying outlooks and behaviors. Topics include cross-cultural studies, historical overview (England had a death penalty for homosexuality until 1861), origins of sexuality, the quest for acceptance, and contemporary controversies such as ``outing'' and gays in the military. Statistics (even a lowball figure of 1% of the US equals the population of Vermont plus New Hampshire) are well supplemented by stories about gay teens, though these are told in a stiff, rather brusque style. Also, when discussing so-called homosexual types, the authors seem to list the more bizarre ones first. Otherwise, informative and incisive. Source notes; resources; index. (Nonfiction. 12+)