I listened to this book on disk with my kids, 12 and 8, which I felt was fine as I knew many of their friends had seen the movie. It is a wonderful book, with some very good themes -- it was good for the kids to hear about kids who were lucky to get one gift for Christmas, who had serious chores that needed to be done without exception (including Christmas,) and who dealt with bullying and hard times using their own smarts. It even touched on the different sides of religion and, of course, the death of a best friend.
My biggest issue with this book (aside from the fact I failed to read the back and therefore didn't realize until half way through that one of the main characters was about to die) was the part about Christmas. My 8-year old was a little confused when the author talked about how the parents couldn't afford to give the kids more than one gift from Santa, and I skipped the next chapter when they started talking about how sad it was that the little girl's hope in a guy in a red suit was "sad". I did some fast talking about how odd it was that the parents were so worried about gifts when Santa brought those with him, then moved on.
Most of the other issues can be worked with for any age over 8 or 9, as long as the parent is willing to go through each issue either ahead of time or at that time, but wait until they're past the Christmas issue!