Well. Some books need to be banned depending on their age/maturity level. My DD (7 now) finished HP series and moving on to other young adult books. She was talking about the girl with the dragon tattoo before the movie came out. I checked the book and it has a lot of adult contents and had to nix her plan to read that book.
I wish they have rating system like movies.
Some book stores like B & N and some libraries have rating system depending on age (supposed ability) but it doesn't really apply for our GT kids.