There will be spoilers. You have been warned.
The first third is a little slow but shows some promise if being a bit heavy handed on valuing individuality over popularity, but it's kind of downhill from there.
You know, the aliens who want to murder most of us and enslave the rest? Boy, they sure are evil, but the worst part is they are atheists. Fortunately for us, since they don't have a god, their superior numbers and weapons can be defeated by their fear of death. (Our heroine, on the other hand, takes the time to pray in the middle of a battle.)
I'm not even going to start ranting about the anti-technology rhetoric.
I don't really expect a great deal of depth out of a kids book, but come on.
I can't believe a book where Baba Yaga suggests teaming up with Darth Vader to save the world could go so wrong.