What Book Shocked You and Your Friends With a Secret Sex Scene?

When you were reading a book, as a kid, did you ever stumble across a little more than you were expecting? Did your friends let you in on the secret? Genre books often come with a secret sex scene. Which books surprised you?

When I was in school, the Clan of the Cave Bear series was on the shelves of a lot of my friends, and the shelves of the library. The series is about a young homo sapien, Ayla, who is raised by neanderthals. The covers of the thick novels feature pristine forests and cave paintings. You'd never know that they featured 20-page sex scenes. But we knew. Just like we knew about a lot of other books. One kid would read a series like Clan of the Cave Bear and be astonished to find some steamy stuff. Then it was whispered about and passed from hand to hand, like a juvenile version of Lady Chatterley's Lover.

Genre books are particularly good at secret sex scenes. Innocent covers and plenty of wordy padding kept them from being scrutinized the way adults scrutinized the more conventional teen books. I remember being surprised when reading ghost sex in Lasher, by Anne Rice, but the book that gave me the biggest shock - and had me thinking "surely he had to fade to black sometime soon" - was So Long, And Thanks for All the Fish. It was nonstop science fiction comedy and suddenly there's a flying sex scene. Oh, that book got passed around. What books surprised you and your friends?