I've heard that the movie deviates almost unforgivably from the book. If that's the case, I can't speak for the book but the movie script looks to have been written by a high-schooler, at best.
The movie is riddled with clichés: Main character with a dark inner battle raging due to prior decisions made (boring!). People (and armies) showing up just at the perfect time (forgivable once, not around the 5th time). Bad guys who couldn't hit a target 20 feet in front of them while shooting an automatic weapon (man those guys suck). And the ultimate "faked death with poison/paralysis" scene (wow that whole scene was bad).
Throughout the whole movie the main character (the annoying tom-boy girl), Tris, keeps being painted as "tough" and "deadly". She is neither of these. In fact, she is quite laughably the opposite. Could her personal trainers not put her through some weight-training classes? (Her hairstylist was definitely present as her hair looked like she just stepped out of a Hollywood salon right after the scene where she cut her OWN hair with a pair of rusty scissors....) It looks like she couldn't even do 10 push ups yet she was fighting people and saving people falling over ledges with ease. But she looks like a huge wuss! Her little girly grunts and squeals she made when fighting or doing "action" made me bust out laughing. And the scene where she breaks through the glass is meant to be bad-ass and instead just left me hoping she would bounce off the glass and fall flat on her back (man, I wanted to laugh so bad).
And probably the most unforgivable part of this whole movie was how POINTLESS everything was. Examples: They fight the faction-less on the train, killing several and doing serious damage to many more (not really sure how because Tris fights like a sissy girl). Then the main character, Four, says his own name and the leader of the vagabonds through bloodied teeth is like, "Oh we cool bro. Never mind you just head-butted me in the face and killed my friends." (the Hell??) (Oh and Tris's brother is a huge pussy). They continue to fight hard and kill people to narrowly escape the perfectly- uniformed drone guards of the "capital" so that they can go in to hiding. Then the main character just gives herself up. I think it was because the villain was threatening to kill innocent people with her mind control devices (never seen that before), but it doesn't really matter. Then she's given the chance to escape by her double- double crossing 'friend' (didn't see that coming) and yet she chooses to stay to open the mystery divergent box. Well what was the point of anything if you wanted to open it anyway??! I was DYING to contain my frustration. (also, how does the evil capital lady have this perfectly built divergent-box-opening proprietary chamber system, complete with bulletproof glass and mystery-box holding pedestal, just already set up? Does no one question this stuff???)
And to top it all off, the super-secret, must-be-preserved-at-all- costs message in the box, (the ENTIRE point of the movie): "Divergents are cool, don't ostracize them. Oh, and the rest of humanity is living outside the wall. Cheers." What? No one has bothered to check this whole time?????? Gag.
Enough roasting. To conclude, lots of movies, even good ones, have clichés and information that you are just supposed to assume. But this movie was genuinely terrible. Maybe all the people reviewing this with an 7/10+ saw a different movie than I did.