When I was about 14, by best friend found a book in her parents' bedroom: "Love and Marriage" by Dr Eustace Chesser, carefully covered in brown paper. She sneaked it out. We used to hide away and read it together. It was a very clinical volume, and I actually think it mystified more than educated us.
I do remember, though, a section on masturbation - the gist of which, for women, was that if you did, you'd never reach a "real" orgasm. Scary to think of now, but since we didn't have a clue what masturbation was, it meant little!