A bit of a disappointment, compared to Divergent and Insurgent. I'd read enough reviews to more-or-less have worked out how it ended, and that definitely ruined the experience for me. 
 It shares a problem with a few other YA books I've read (yo, Mockingjay I'm very much looking at you), where the big action sequence/ending feels too short and choppy and video-gamey, and as if the author was bored and ready to finish writing. 
 My biggest problem though, is that the text was bloomin' HUGE. I haven't read a book with font that big and widely spaced since I was learning to read (and I feel that the level of vocab in Allegiant, though fairly simple, is probably more advanced than "learning to read"). I almost felt like it was spaced like that in order to make book look longer than it really was, which really irritates me, because I have limited shelf space, I don't need books that are pretending to be longer than they are. 
 I don't know if I'd be this harsh on the book if I hadn't been reading a lot of literary fiction lately, which tends to miss out the big action sequences altogether. 
 (view spoiler)[Plus, the (probably?) sex scene bugged me. I get that some younger readers don't necessarily need all the sordid details, but it was left way too ambiguous for me. It could easily be interpreted as just a pretty steamy makeout session, and given that Tris and Four chose to be in Dauntless, the faction who seem most likely to be up for the most (and most interesting) sex, it doesn't really sit right with me that that's all we got from them. 
 And, while I'm using spoiler tags, I wanna complain about how unemotional I was about Tris' death and Four's reaction. It's ridiculously easy to make me cry for character death's. If I have a fairly "ehhh" reaction, then either I hated the character, I didn't connect with them, or the writing could have been better. In this case, I'm fairly sure it was the last one (which resulted in me not connecting with Tris). (hide spoiler)] 
 Actually, I think this review sums up a lot of things I hated, and touches on how clunky a metaphor the whole GD/GP situation is. So pretty much just go read that one.