I originally bought Divergent and Insurgent on a buy one get one half price deal from a local Waterstones bookshop, and if I hadn't got the two of them at once, I most likely would never have picked up Insurgent after being less than thrilled with Divergent.
As it turned out, I did actually like Insurgent a little better. I think it was because there was more world building, and you got to see more of how the other Factions functioned, and the plot was more developed than just Faction training.
I didn't actually like Triss much at all in this book, considering how bad ass she was at the end of the first one, I found her very wooden in this book. And I still don't buy the romance with her and Tobias at all. Its a little weird, even though I wasn't all that blown away with the main character, I thought it was a much better plot than the first book.
And I was never going to bother with the final book, but now I have to know how the whole thing ends.