Left to my own devices, I wouldn't have let Elizabeth start reading Harry Potter until she was the same age as Harry in the books. The first few are fine and both Brendan and I enjoyed reading them greatly ourselves but it seems to us that they get less and less age appropriate as they go and there are many, many other books that we'd prefer our kids read first that are both great reads AND age appropriate.
It is of course possible that we are slightly on the overprotective side when it comes to media consumption, but I've never understood the hurry to introduce kids to things like Star Wars or Harry Potter.
This of course drives Elizabeth batty as she was the only kid in her Sunday School class not to have seen the latest movies and I'm assured she's the only kid "not allowed" to read Harry Potter.
She was obviously thrilled when it was assigned for karate book club, and we decided that not allowing her to participate would probably be cruel. Needless to say she absolutely LOVED the book and begged to keep reading. We decided that she could go ahead and read the first three books but would need to stop and wait a bit longer for books 4-7.