I've had to read two Toni Morrison books in school, Sula and Beloved. Neither were as graphic as this one, but they weren't very good books (in my opinion) either.
I did have to read Clan of the Cave bear in 11th grade, and that book does have several rape scenes, but I think they were much more tastefully done than this one, and there is so much more to the book that those few scenes aren't the focus of the entire story.