Honestly, I was disappointed with this book. It seemed to have lots of hype, and a movie! It must be really good, I thought. Sometimes it's hard to live up to the hype. 
 There is a thing called suspension of disbelief, and good stories don't strain it. This book strained my suspension of disbelief to its limits. With little things, and with big things. Some examples - 
 Little things: One character wears his missing father's eyeglasses, which are the thick, google-eye kind, to be close to his father, to see what he last saw, whatever. The kid doesn't need glasses, but he wears these all the time. Until one day when he stops because he decides he doesn't need that crutch anymore. I'm sorry, but this is unbelievable. He wouldn't be able to see with the glasses. 
 Big things: There are nine aliens with their mentors who are scattered on earth, waiting for the time when they can fight the bad aliens and go back to repoplulate their own planet, which was destroyed by the bad-guy aliens. Nine, plus their mentors are supposed to be able to defeat the bad aliens when the whole population of their home planet was unable to do so and perished? Unbelieveable. 
 There were other things which bothered me in the book, too. In the last big scene the good guys are running around, hiding in the school - "We have to get out of here." So they run for the woods. Yikes! Bad guys! So they run back to the school. "No, our only chance is the woods, but some of us have to stay in the school." Gaa! And the scene, although it is supposed to be action-packed, dragged on and on, at least for me. 
 I'm sure there are people out there who can stretch their suspension of disbelief to great limits. This book is for them.