Although this one was brutal it was my favorite of the series. Only with the completion of book three can you see the overarching structure of the Hunger Games.
*** Some mild spoilers follow ***
Each of the first two novels ends with the horrors of the arena and the third novel ends with the horrors of the rebel raid on the Capital which is every bit as terrible as a Hunger Game. In each instance dozens of people die for no good reason and it all ends in rage and futility. Katniss entered the Games to save her sister and in the end she cannot save her, closing the circle of futility. Each novel reaches a point where Katniss decides to kill herself and each time is pulled back from the brink by her concern for Peeta. I say concern and not love because the desire to protect people is about as close as Katniss gets to love. I also say Peeta and not Prim because each time it is really Peeta that pulls her back from self destruction.
Peeta really comes into his own in Mockingjay. In the first two books he is a mix of sad-sack and too good to be true. The twist Collins pulls with Peeta this time is truly twisted. The extremity of how much Katniss has been manipulated through the course of the story comes clear in Mockingjay, she has gone from being a puppet of the Capitol to being a puppet of the rebels. Like in the first novel Katniss ends this story with an act of defiance that shocks the system, but even this final act of rebellion is the result of manipulation. There is some actual character development in this series, Katniss, Peeta, and Gale are all changed significantly by the end of the story, which is kind of rare in YA fiction.