Amazing book. Although the ending wasn't that excited, it still made me grin. It's not all about the execution there, but throughout the story. I slowly began to loathe the antagonist somewhere around the middle, so the way the book ended was good enough for me. Take it with a hint of salt, if you'd like.
I love the narration in the book, and it really does fit with the "14 year old girl" voice. It's really easy to embody her, especially since she was a normal girl who happened to be victim to something for sinister.