When Deborah Rudacille learned that a close friend had decided to transition from female to male, she felt compelled to understand why. <br><br>Coming at the controversial subject of transsexualism from several angles–historical, sociological, psychological, medical–Rudacille discovered that gender variance is anything but new, that changing one's gender has been met with both acceptance and hostility through the years, and that gender identity, like sexual orientation, appears to be inborn, not learned, though in some people the sex of the body does not match the sex of the brain. <br><br>Informed not only by meticulous research, but also by the author's interviews with prominent members of the transgender community, <i>The Riddle of Gender</i> is a sympathetic and wise look at a sexual revolution that calls into question many of our most deeply held assumptions about what it means to be a man, a woman, and a human being.