I'm going to be honest and say up front that I haven't read any of the Divergent books but so far have seen the movies.
I did saw Allegiant recently and not entirely sure if I like the film or not.
I found that the VFX were a little similar to the VFX in the original Spy Kids films. TBH the VFX in this film is only slightly better the VFX seen in Spy Kids.
I also found the character development lacking in a lot of ways. The characters also seemed a little bit one dimensional. I also found the acting a bit bland as well. For the most part, I felt the actors were just turning up because of the pay check and didn't really put much effort into their characters.
I thought the set design was really good. As it does show that the story is set years after some sort of disaster. The camera work was really well done as well. I liked how the editing was done for the film as well.
Even with the films problem's the film is still working checking out if your are a fan of the books.