I was a little concerned after reading some reviews saying that this book wasn't as good as the first one, I have to disagree, I found Insurgent to be as good as Divergent was.
I felt that Tris/Beatrice/whatever she would like to be called at whatever point, was developed well, how she felt about things, the moments she suddenly realised things, they were all in line with how a person might feel in those situations. The one problem I had with all of the characters was that no one seemed really effected by any of the deaths, I realise that the rebel-war thing doesn't lend itself to grief, but it was a little unbelievable.
I had read complaints about how the big reveal at the end wasn't worth it, I can admit that I did find the reveal predictable, but ultimately it was really well built up and there are still questions that I want answers to, which unfortunately I have to wait until October to find out!
There were points in this book where I was surprised, namely by who betrays Beatrice, did not see that coming! Though I won't say any more about that in the interest of spoilers!
I also really liked the fact that Tris/Beatrice's and Four/Tobias' relationship is far from perfect, I suspect if someone looked into it they would find that they argued more than they kissed in this book!
This book has really left some questions, and there was an issue resolved that I thought would take up the entire trilogy has kind of made me slightly confused and interested in what is going to happen in the next book! Bring on October!