This is the third book in a series by Rick Yancey. The first book was made into a movie last year, and is titled The Fifth Wave. I have finally gotten around to reading the third book, The Last Star. If you haven't seen the movie, it is an apocalyptic story. The world was invaded long before the first wave hit humanity. The invaders co-inhabited the bodies of humans and waited silently to take over the earth. As I read the third novel, I am unconvinced by the argument that the invaders have come for our own good. The idea that humanity is better off without feelings and empathy is a hard argument for the destruction of an entire race.
If you aren't familiar with this series, it is an exciting story as young people are left to save the world. You might also try other books by this same author including The Extraordinary Adventures of Alfred Kropp.