My full review is here on my personal website. I'll post a few excerpts here, though:

4.0 out of 5.0 stars

The very worst thing about this book is the school Artemis is sent to. It ust bugs me, for some reason. At any school I’ve ever attended, if you see the school counselor, you can’t simply call them idiots, walk out, and then fake a call from mom to get you off the hook. Any school school counselor I’ve ever known would be calling every few days making sure everything was all hunky-dory even when mom says “don’t call.” Especially for the kids they don’t like so that they can’t be accused of playing favorites.

The very best thing about this book is that Colfer never takes the easy way out with character redemption. There is no “Artemis thought about his actions, realized the fairies were right, and decided to change.” Artemis is still a bad little genius who is starting to change, but is taking his own sweet time about it because he certainly loves his crime. :-D