I agree with everything Maciek says about this book, but I'm going to be a little more gentle with my rating because it's self-described as a book for teens.
I'm the type of reader who's never complained about too much explicit violence and/or sex in a book. I went into this series expecting there to be little of either, given that it's aimed at the teen crowd. My predictions were correct. There's a lot of sappy angst that seems to go on and on, but as I recollect my years as a teen, they were sappy and full of angst and seemed to go on and on.
What I liked about this story is that the protagonist is a capable young woman, and the plot moves along briskly enough that while I didn't get very much visceral enjoyment from the story, I did enjoy the tactical plot developments. I liked enough that I read the rest of the series, anyway.
Also, my young cousins have all read the books and now I have something to talk to them about.
I'm knocking a star off of each of the books in this series. In retrospect, there's nothing in these books that stick with me. No interesting ideas or turns of phrase that warrant the effort of retention for repeating in front of a different audience to make me sound more intelligent than I really am. The best conversation I got out of these was with my wife, "The best way to enjoy the series is to stop after you finish the first one."