As the 20th century began, Paris was a mecca not only for art but for sex—especially in manifestations hard to find elsewhere. Mel Gordon’s glibly fascinating, profusely illustrated account uncovers several subcultures that flourished in the shadows of the City of Light, including officially sanctioned prostitution houses and gay clubs subjected to periodic police raids. The most fascinating chapter concerns the wartime Nazi occupation, which proved especially profitable for prostitutes, male and female. Selective retribution against sexual collaborators after the liberation of Paris was swift and terrible.