Insurgent continues to tell the story of Tris as she takes on her identity and an "ideal" society in order to save herself and justify, in her mind, the death of her parents. This book stays with the same story line as the first book giving more room for Tris's own personal struggles to come forward. Personally, I was yelling at the book sometimes because for someone who is so logical most of the time, Tris does some pretty dumb things. Selfless, "Abnegation", or not, Tris is not thinking of anyone when she embarks on a couple of her self proclaimed missions. Also, there is obviously a good mix of young romance in the story as well with Tobias/Four (which is always a good idea, in my mind, for any book) although I did not feel it was as prominent as it was in Divergent.
If you loved Divergent, then Insurgent is definitely (and quite obviously) the next "candor" book to read. I loved it and can't wait to start reading Allegiant!