Divergent made for a fast read, and as soon as I finished, I ordered the next two in the series.
The book has a definite love/hate division among readers. I think maybe the love faction came to the book without expectations and enjoyed the thrill of all of the action--and this is an action filled book. Those who hate it may have heard all of the positive reviews and then been disappointed that it was not what they expected.
Roth has created a world that doesn't quite work. The Factions idea doesn't seem plausible to me. The thing is, though, somehow she makes it work as long as you don't spend too much time analyzing it. The physical world doesn't quite work either, especially the arrangement of a city that has different Factions living in completely different surroundings. Any visualization of this world as a whole has to be purely from your own imagination, although Roth does give very brief descriptions of the areas occupied by the various Factions. The overall view of the city-world doesn't really exist.
The Dauntless home ground, where most of the story is centered, has little detail for such a complicated place, but again Roth manages to keep this from interfering with the pace of the story. It works, if you let it, because of the characters and the action.
I could let all of this slide because I was drawn into the story. Part of my brain was perfectly happy to ignore the flaws. The one that bothered me the most was that the Faction transfers went through such a short initiation. They learned how to fight, shoot, handle knives, etc. in too short a period of time. Tris mentions building muscle in a week. The transfers and initiates who survive the cuts become skilled athletes and crack shots within a month. In a month or so, transfers from Factions that have no physical activity become super brave and can run, jump, fight, and handle weapons with the skill of soldiers.
None of the above problems, and there are more, managed to keep me from enjoying the book. It was exciting and entertaining and fun.
Insurgent - Still exciting, but not as good as the first book.
Allegiant - Oh, dear. First problem--the two previous books have been from Tris' first-person pov. Now, there are frequent switches from Tobias to Tris...and the voice doesn't sound any different, so you have to be careful not slip back into thinking it is Tris speaking when it is Tobias. A weak finish for several reasons.