I like Four. I liked him in Divergent trilogy and I like him either now. But I'm not convinced about this book. With prologues is always one of the biggest problem - aren't particularly surprising, because everyone knows what happened next, and a lot of things from the past, it was already mentioned. And so it was in this case.
The whole 'Divergent' trilogy was for me very interesting and I really wanted to know what was before, so the first part of the book, when we meet Tobias, before he meets Tris was pretty cool, but there wasn't a lot of things we haven't know from Divergent. And when the action began to overlap with Divergent, it got boring. I expect that I will know more thoughts and feelings Four, but everything was there such a barren and obvious that I have a feeling unsatisfied.
I think that the book didn't bring much to Four characteristics, and to complete the entire trilogy didn't bring almost nothing.
I rate for seven only for the sake of sentiment to Four. The whole deserves in fact fetched six.