I had to struggle a bit with this one. 
 The style is really simple and dry which, in the beginning, led to think the story more childish than what it actually is. 
 Moreover the basic concept underlying the dystopian world in which Divergent is set doesn't really make sense:namely, in order to prevent future wars to happen society has been divided in five factions which obsessively promote five distinct virtues, sometimes in contrast with each other. 
 Now, I suppose there are many school of thinking about how to reach universal peace and not an univocal solution but honestly promoting non-communication and exacerbate personal differences doesn't seem such a good idea to me. 
 Anyway, Veronica Roth seems to think this is a brilliant solution therefore she divides the inhabitants of her dystopian Chicago into the factions of Abnegation, where selflessness is pursued to the limits of a monastic life, Dauntless, where every heroic (or just stupid?) acts are encouraged, Amity, which pursue friendship and good relationships, Erudite, who places knowledge above everything else and Candor, which believes in blatant honesty in every circumstance. 
 Each faction believes that by promoting its virtue, all wars and personal contrasts can be defeated. Well, I can understand how being honest or unselfish could help human coexistence but what about courage? It seems to me that Roth is stretching things a little bit,again, just because having a Dauntless faction is fundamental for giving her story the amount of action it needs. 
 Set this aside, the author does manage to make her story worth reading through a good mix of an interesting heroine and a compelling plot. 
 Tris was born in Abnegation faction but she never really fit in. All the selfless actions that her parents and her brother seem to manage so naturally are for her a struggle. Growing up she has always felt the pull for a different life, one less submissive and more daring. Now that she is sixteen she will have to pass an aptitude test and decide in which of the five faction she wants to spend the rest of her life. Needless to say, defying the ostracism of her family she chooses to be part of the Dauntless faction. But things are not so easy: first of all before being accepted by Dauntless all initiates have to pass a hard training which will push their physical and psychological boundaries; then Tris' aptitude test gave an ambiguous result, which could put her life in danger if discovered: she is Divergent. 
 This is where Roth's novel shows its value, that is in its good rendition of the struggle every teenager has to experience in order to find his/her place in a society which likes to channel us in per-defined cliches and doesn't appreciate who breaks the mold and affirm his uniqueness. This is a kind of problem which anyone experiences in life and not necessarily just when growing up. Preserve those traits of our character which makes us different while still fitting in a group of friends and peers can be complex and lead to a lot of suffering. Tris is a good heroine from this point of view: she is smart and courageous but also stubborn and impetuous, compassionate but not unselfish and not everybody is prone to fall unconditionally for her. Moreover she is not a blond barbie hidden under an ugly pair of glasses but she is actually a normal girl, non particularly pretty or attractive. Her love story with Four is a tender and sweet, even if a tad predictable. 
 Many have complained that the book is almost totally focused on the training part but those who read the story know that there is nothing dull about this training, on the contrary it can be as good as a real war. As a matter of fact Roth has a knack for action, her stile despite being simple is certainly compelling and she has no qualms about introducing violence in her story. The world invented by Roth is made of violent and unscrupulous characters who leave more than a victim behind them and surely it is not for the faint-hearted. 
 The result is a gripping novel, well paced and utterly captivating and I actually devoured it in a couple of days, despite the initial doubts. 
 It is true that many aspects of the story are left undeveloped, especially where it comes to the details of this dystopian reality, for example it is never explained what led to the present social structure or how it survives and two of the five factions, Candor and Amity are left on the background and practically nothing is said about them but this is a typical flaws of books like this which were conceived from the beginning as a unique trilogy, so I expect that these blanks will be filled in the next volume. Of course this is not an excuse for the lack of in-depth analysis but it makes it understandable and tolerable; besides I like a writer who doesn't spill all her secrets at once. On the contrary, I found somewhat irksome the message the book seems to imply about culture, that is that the pursuing of knowledge is a form of arrogance and should be limited by certain boundaries while all members of the Erudite faction are depicted as cold-hearted and power-obsessed. It all sounded a bit to "biblical" to me, but maybe I'm misinterpreting the author's intentions, I'll see if she can prove me wrong in the next chapters.