I have read the full series and seen all of the movies. This is the most disappointment I have felt with this entire series. The first book and first movie were wonderful, and the second book was good, but not so much the movie.
The only bad book out of the entire series is this one, which is inconsistent from the rest, and is super slow with a build-up at the pace of molasses. If you want a lot of not-so-entertaining dialogue with an unsatisfying ending, this will be your favourite book. An unpopular opinion is that the Allegiant movie is better than the book. It at least adds some action and a cool environment, something new and somewhat entertaining.