I think I read that in like grade 7? Was it a really thick book about a brother and sister who's step mother fed them rat poison on their donuts and the brother and sister got intimate with each other?
@saintsong No. It was written in the 1800's. A man gets married and discovers that his wife is insane. However, divorce is not possible in that society, so he keeps her locked in an attic.
I think you are thinking of a more contemporary novel.
