Full disclosure: I read the book before seeing the movie. Sometimes that doesn’t make much of a difference. However, this time it did.
Going into the movie I expected some differences. It’s hard to take the complexities in a book like Allegiant and adapt them to the screen. What I did not expect was for them to largely ignore the depth of the book in favor of action. Huge parts of the book were left out – characters who had major roles in the book were reduced to tiny parts. Some of the heavy interpersonal relationships and tensions disappeared. We lost a lot of character development.
Speaking of the action, some of the green screens were just terribly obvious. I get that there are limitations when trying to create the torn up landscape of a war-torn Chicago. But this was… poor. The fighting scenes were fairly well-done, but the larger placement shots were not good.
The pace of the movie is very fast. Two hours goes by in a whir. I assume some of that pace is because they skipped the character and story development. Those would definitely have slowed down the progress of the movie. I don’t know if it was worth the cuts, though. I suppose if I hadn’t read the book, I may not have noticed.
Overall, it comes across as very superficial, with so-so visual effects. I would probably still see the movie, just so I could feel that sense of completion. Just don’t expect a lot.