Tris and Tobias have left the city and all of it's troubles only to find out that they aren't alone in this world. There are others and Chicago was a social experiment spanning generations. There are two types of people, the genetically damaged and the genetically pure. This book is just a repetition of the first two books, but on a grander scale.
Compared to the first book, I would have to say that this book is wholly unoriginal. The story of Tris and Tobias and their revolutions is just the same crap, different day. The book was predictable if you just thought about it for more than 5 seconds. If you weren't looking for a book to think about, that's fine, I'm sure you enjoyed it. I read books like that sometimes too. No worries. Unfortunately, I thought about this book, and it ruined it for me. Overall, I would say that this is just a repetition of a story that the author knows works. The writing doesn't get better. I just wanted something different, and I was disappointed. The series itself is a fun and easy read if you just want to read something and not delve too deeply into it. So for that, I give it a thumbs up. For the actual writing and plot... it leaves something to be desired.