It takes a while to really get going, but when it does it's good. I especially loved the strange, complex character of Cassie, and the tenuous rules and networks built around the wizard community.
Felt more like a novella than a novel, and I really wish it weren't a stand-alone book. Too many good ideas to cut it off so short, and leave so much unresolved.
I also disagree with the reading the one spoiler reviewer had: there is definitely a real fantasy world here, it's just a very hard one to accept, and so takes a lot of strength on the part of the wizards to do so.