For a long time, I resisted the pull to read the popular Divergent Trilogy. I had already been disappointed by The Hunger Games books, and I have read too many other dystopias that are good to waste my tolerance for the genre on a poor facsimile. However, I did decide to give the first book a chance. I read it, and found it to be very interesting and compelling, and purely for reasons of completion, decided to read the other two.
While I found Insurgent tolerable and even interesting, it was really fast paced, which made it difficult to cram all of the character development Roth wanted to fit in into the novel. I read Insurgent and Allegiant back to back, which might have exacerbated the obvious and problematic differences in the latter. Roth’s explanation of “We’re all just rats in someone’s locker” falls completely flat. If you replace every time they say “science” or “genetics” with “magic” “voodoo” or “energy” the story would be exactly the same! Oh, by the way, your whole world is a lie. And all of the characters reconcile themselves with this pretty damn quickly! The dual perspective is a bit jarring, it’s a bit distracting from the narrative flow. It is nice to see things from Four’s perspective for a change, but he and Tris seem to think fairly similarly. The world Roth created outside “the experiment” doesn’t make much sense. How can so few people be rebelling with any effect? Surely someone remembers the countless other wars fought in the name of equality? My other problem with Allegiant is that I can’t think of it ending any other way. With most endings that upset me, I can just make up my own ending and be happy with that. But with the story that Veronica Roth was trying to tell, the ending she wrote is the only one that I can see. Of course Tris would never willingly let someone die for her, if she could save them and sacrifice herself. When Tris tried to die for everyone in Insurgent, she was saved, because she was trying to sacrifice herself for selfish reasons. But when she died to preserve her city and change the world that she had just discovered, she did something entirely in character with the person she had become. But it didn’t stop me from just bawling like a small child.
The problem is that Roth gets you very invested in Tris and Four’s relationship. So many people die in the course of the books, but Tris was the main character. We heard her thoughts and knew her deepest feelings, we connected with her. If she had not sacrificed her life for her brother, it would not have not been in character, but this is the story that Roth chose to tell. Tris and Tobias have their happiness but for a little while, it’s like teasing. They have so little time together when they’re just happy and get to be themselves. They’re always fighting a war that they were born into, and later a fight that they don’t even have ownership of. While I don’t think the ending is fair, life isn’t fair. Neither is death. Who cares? Tris did the right thing. She did the only thing she could. There was no ending to this book that had her live. Tobias honored her by defying his fears. He reconciled with his mother, and stopped the war. He did what he had to do, and so did she. The ending isn’t fair to Tobias, and I can definitely see him developing a drinking problem later in life, but it was the only ending. And, despite my grief, I have accepted that. 
The Chamber of Spoilers 
The real problem, though, is why Caleb was ever in a position to be the sacrificial lamb in the first place. Think about it. Why did this even come about? What were they doing? I’ll tell you what they were doing: Concoting a completely ridiculous, unnecessary, and fully out-of-character mission that serves no purpose other than to invent an excuse for Tris to sacrifice herself. And of course she did. What else would she do in that moment? But there was no logical, believable or necessary reason for that moment to even exist. The entire situation was completely contrived just to force Tris’s hand. The author knew this was how the story needed to end, and she twisted and manipulated and contrived everything to create that ending. It was like watching a death in a Final Destination movie, where everything just oh so conveniently conspires to cause a character’s death like someone is behind the scenes pulling the strings. Only thing is, in those movies, someone IS pulling the strings; Death itself is a character in the story forcing these things to happen. But in Allegiant, it is the author who interjects her hand in the story and manipulates everything to suit her external purposes with no regard to the internal logic of the narrative. It’s really badly written and unfortunately negated whatever purpose the ending was meant to serve, because everything that created that moment was fake.