I wouldn’t say any book taught me much about sex. But Ellen Hopkins books were really popular when I was in middle school/early high school & they cover a range of darker topics (addiction, sex work, etc). My friends & I were the book crowd so we read a lot of books that were probably a little too old for us. So these books I would say maybe opened my eyes to the darker side of sex, not the super romanticized things that you see on tv. If that makes any sense