I'm halfway through book three right now. You may have heard a rumor that book three is not up to the standard of the other two.
Well, I hate at some levels to call a fellow author out in public, but in this case it feels warranted.
Books one and two are written in first person, present tense, from the viewpoint of the main character (much like Hunger Games, but Suzanne Collins did it a bit better - then again, I'm personally twitchy about first person present).
In book three, Roth switches between the viewpoint of the main character and the viewpoint of the love interest - still in first person present.
I've done switching viewpoints. Some stories need it. The problem here is that although Tris and Four are quite different characters, in the book they sound exactly the same. Exactly the same. I (and my husband has the same problem) have to keep checking who's chapter I'm in.
So, the lesson to other writers - if you're going to switch viewpoints in first person, be very careful to make the characters sound and feel different. Otherwise you're just going to confuse your reader.
Sorry, Ms. Roth.