This is a great post Apoc book and if you like that sort of thing you will like this one. I have heard people call it a dystopian but I don't see that In this book, at least it does not follow the norm of most dystopian and that is fine with me. I also liked the setting of the book and the thought of aliens being a part of it, it added a nice element to the story as well.
I did enjoy the characters a lot. There are so many characters, and not all of them are good people, which is awesome because I feel like this allows readers to touch on every emotion. Of course I have to say I loved Todd and Viola the most. I do feel like they were pretty grown up for their ages though, and I expect that is due to the situation they find themselves in.
Since I enjoyed this one so much and the cliff hanger that it ended with, I have the other 2 as well and I will be reading The Ask and the Answer very soon. Also in each of these re-mastered books, you will find a short story in the back pertaining to the series. So that is a nice touch I think as well.