It is basically like the Hunger Games, apparently, if you have watched that. I haven't. Anyway, it is basically set in the future in this place that is literally walled off from the outer world. They all believe that there is nothing good outside those walls. And, within the walls exists a system which they think is the best way to remain the best kind of society. This is to divide the people into 4 different groups based on their personality. Or was it 5? I don't remember. I don't remember the names, either. But basically, there is the group that is kind & selfless. The truthful ones. The calculative, logical ones, the daring ones(Dauntless). That is all I think. People follow their family's group until they are of age when they have to take a test which gives them which group they best belong to. But they are still free to choose any other group during the sorting ceremony (HP term, but I don't remember what exactly the term here is). But once they choose there is no going back. And, if you are in a different one from your family, you don't even get to see them. Group before blood or some such thing. The twist comes when there are people whose test shows they can belong to more than one group. They are called Divergent. This doesn't settle well with the set up because they fear these Divergents, as they think they can cause chaos. Hence, they are being hunted. The heroine happens to be a Divergent, but has to hide it. Her parents are in the selfless thing, while she chooses Dauntless. There she meets this guy, who is a trainer, called Four(for 4 fears, the least that anyone has). Then, it is about what happens once she joins Dauntless & the Divergent hunt continues.