A few issues so far:
1) Tris learned to shoot and handle a gun way too fast. There's no way she could do that so quickly. (Gunsmith's daughter here. Trust me, I know.)
2) She's awfully judgy of someone else crying, when she's doing the same damned thing.
3) I'm getting tired of her being so fake tough. It's annoying. Butch up or shut up. You chose this mess.
4) There needs to be more world building. I had to look up where the Sears Tower was to get an idea of where in the world this was happening.
And this is just a note about all dystopian fiction: why does everyone think that when the world falls apart, we all split into know-nothing factions/districts/casts? It makes no sense. And this "Dauntless living in a cave" thing is the dumbest thing I think I've read yet. Does living in a cave make you tougher? Or just stupid? I think the latter. Dwayne Johnson is pretty damn tough, and he lives in an effing mansion.