My brother was 7 and tried to take Philip Pullman's The Golden Compass out of our school's library, but the school librarian wouldn't let him. She said that he wouldn't understand it and then he'd lose confidence in his ability to read. My dad had to come into the school and tell the librarian that any book my brother wanted to take out she should let him take. I could not believe that a librarian of all people would prevent the distribution of good books.

I think there are books which make more sense at one time of life or another, and I think that if I were a parent there are definitely books I wouldn't buy my 10 year old, or let them read if a copy was lying about. That said, I don't think there's a hard and fast numerical answer to this question. It's not about age, it's about maturity- which is a wishy-washy non-answer in all honesty, but it's also the truth. If a child (or a person) is earnestly willing to consider the theme of a book, and to apply themselves to it, I don't see a reason to keep them from reading it, barring pornography.