Exactly how steamy is this story?
R
Jack is five years old and his mother is raped almost every night within earshot. Traumatic? Yes. Steamy? No. But it's still something that no one of that age (or any age) should have to deal with, so we're stamping this with the ol' R-rating.
All the sex takes place in the dark, and Jack doesn't really know what's going on. He says, "I always have to count [the creaks] till [Old Nick] makes that gaspy sound and stops" (1.441). Um, gross. Cover your eyes and your ears for this one.
Aside from that, there are a few instances of innocent nudity. Ma and Jack often bathe together, Jack's "Silly Penis is always standing up in the morning" (1.310), and Jack learns an important lesson about male and female private parts in the bathroom at the mall. That's all part of growing up.