This is going to be kind of a bullshit review. I say that because it's usually how I to respond to other movie reviews that let some single element of a movie derail all the other potentially good aspects involved. Usually, I can get past this sort of thing. Divergent defeated me, though.
Divergent's premise doesn't make any sense. I had trouble understanding it not only during the film's promotional phase but also during the many unsolicited conversations I had about it with my kid, who really likes these books. Now that I've seen the movie, I am sad to report that I understood the premise correctly the whole time. It's just really stupid.
In some kind of future after some kind of war, people are divided up into factions. There are only five. You can be smart, honest, brave, something or something else. An all-important mandatory test helps you discover your primary personality trait (out of the five). This trait defines you to such an extent that you are a robot slave to it. If your faction differs from that of your parents, you must leave your family. On the other hand, if you disagree with your test results, you can feel free to totally ignore it and follow your heart.
Shailene Woodley (like all actual humans) has a combination of all five traits. This makes her a Divergent, something that ultimately has no meaning at all since everyone she hangs out with displays a full plate of human personality traits, however blunted and quickly drawn. It's all really just a way to make her special narratively.
Afraid people will discover she's a full human, she still joins a faction and spends most of the movie trying to hide her true nature. Her crew is called Dauntless. They have no fear. Except all of them are driven by fear. They might actually be the most scared people in the city, considering how often they try to prove themselves with wimpy stunts. For instance, instead of getting on trains at actual stops, they run alongside the moving cars and jump on. Like hobos. When it's time to get off, they leap from the train car to a nearby rooftop. It's pretty close, so they could probably just step off casually, but they prefer to jump and land with a badass rolling motion. When it comes to being tough rebels who play by their own rules, this Dauntless crew ranks right up there with the gangs from West Side Story.
90% of the film focuses on Dauntless training. Shailene Woodley has to develop her Dauntless skills lest she spend the rest of her life as a hobo and be forced to run alongside trains out of necessity rather than youthful fun, an outcome she's scared of (classic rookie Dauntless mistake!) She makes friends and enemies of her fellow recruits and even falls in love with her head instructor, who wants a full personality so badly that he tattoos a picture of each trait onto his back. That actually works, by the way. It's why I have the word "big" tattooed on my wiener (I would have preferred the word "massive" but it turns out this doesn't actually work as well as I just said).
Eventually, the fact that all these people live in a dystopia run by an evil blonde lady becomes a factor, and it is only at this point that the film finally wakes up and does something. This last bit, however goofy, offers decent kiddie-action and at least gives the film some of the stakes and plot movement lacking in the whole "Will Katniss Jr. pass her Dauntless final?" issue.
You can see how this appeals to its audience, though. The faction system allows young people to imagine which group they'd belong to, while also giving them plenty of room to imagine themselves as Divergents as well, since I assume most of them do possess a human personality. The film has a heavy-petting romance and involves living with buddies for months, far away from the gaze of any parental units. It's all a nonsensical fantasy, but I can understand the appeal. Plus, there's a chance the sequels might have interesting mysteries to solve and a much wider world to explore.
This one, however, is just too small, too ridiculous, and too uninteresting to enjoy. You will likely find yourself asking some random kid next to you "How much book is left?" and their answer will bum you out. That's what happened to me, anyway.