This is the last in the Divergent trilogy and well worth getting through book two to get to this one. I enjoyed Divergent, I rather like the young woman as political vigilante in a dystopian future genre for young adults that seems popular right now. Insurgent went off the boil a little bit, the plot holes that are forgiveable in books one and three are more annoying in book two. In Allegiant we find out why the city was as it was and what was going on beforehand and many of the loose ends are tied up.
In this book we hear a little about Tris’ mother. I believe we can read some short stories about Four if we want more of these characters, but I would much rather read Tris’ mother’s story. The prequel to this story would be much more interesting than what the boy goes on to do.
Allegiant is set mostly outside of the city with shady genetic experiments and government cover-ups going on. This one is all a bit more Brave New World or The Matrix than the first two, which can only be a good thing. My major problem with the premise of these books is that people can never be split into five clear personality types. This book clears all that up.
There are still some plot holes. They rationalise the method they choose to save the day, which is essentially the same terrible thing that the bad guys were about to do. And, there are an awful lot of convenient serums that can do all sorts of unlikely things. But if you can suspend your disbelief and remember that this is for kids then you can enjoy it.