The Scarlet Letter
The Scarlet Letter Steaminess Rating
Despite the sex we're sure Hester Prynne and the Reverend Dimmesdale had, this book is more about the guilt, shame, and suffering than the bodice-ripping and heavy breathing. Definitely PG material here, and the only thing that keeps it from being G as far as we're concerned is that who don't want to have to explain to any kids why everyone's so obsessed with who Hester had sex with.
Still, at the time it was written, the novel was a lot racier. Adultery and out-of-wedlock births weren't exactly dinner table conversation. We can see the headlines now: "Young, sexy married woman has child with young, unmarried minister and plans to run away with him after her estranged husband is transformed into an evil, demonic person seeking revenge on his wife's unnamed lover!"
Yep, there's some potential there.