I enjoyed the final book of this trilogy. Finally, explanations are given for the faction set up, which I've struggled to see as realistic in the earlier books. It makes more sense now. 
 Didn't get on with the addition of Tobias' POV at first as it didn't feel all that different to Tris's, but it improved as the book went on. 
 I liked the ending and the wrap up. Far more satisfactory than The Maze Runner series which had similar themes. 
 I nearly didn't bother with this book as the middle book of the trilogy was weaker, but I'm glad I did read it in the end.