Probably ~3.5 stars; this is a good YA pick for fans of adult urban fantasy, but it's not one everyone will enjoy. I definitely am on board for the sequel, and thought this was a creative and unique story. The more I think about it, the more I like this book. My entire review is here: http://cleareyesfullshelves.com/blog/... 
 Jan 2013: 
 ACP was pushing this as "the next Angelfall" at ALA (possibly in an attempt to hide the fact that there's no title/date/etc for the Angelfall sequel). Honestly, though, it sounded very creative and unique.