It is no secret that I LOVED Divergent. It was amazing...and while I really enjoyed Insurgent, it just didn't have that same magical *spark* that Divergent did...
One of the things I liked the most about this book...and simultaneously cursed, was that it broadened our world-view and gave much more depth to whole story. Readers got to learn more about each faction - how it was developed, who runs it and where, what are its principles - and how they interact with each other. It was really cool to see how the entire city worked as a whole.
The world-building felt much more developed here, but in Roth's feeding us so much information, you lose the magic of living directly in Tris' head. As such, I felt that the first half of the book developed very slowly... it was not until midway through that I became really solidly invested in the characters again.
And what Tris and Four go through... I just wanted to reach through the book and hug each of them... There are betrayals, there are massive secrets revealed, there are deaths. I cannot say more without getting all spoiler-y.
Now... all that being said...the end of this book goes out with a BANG! I love where Roth took this, though I was left with some burning questions that I can only hope get answered in the final book. For a variety of reasons, book three is a must read!