Mockingjay by Suzanne Collins

The last book of the Hunger games trilogy. After her rescue by the rebels, Katniss willingly agrees to become "the Mockingjay", a symbol of the rebellion against the Capitol. As part of a deal, she demands that the leader of District 13, President Coin, grant immunity to all of the victors of the Hunger Games. She also demands the right to kill President Snow herself. In a daring rescue, Peeta and other victors are rescued from the Capitol. However, Peeta has been brainwashed into hating Katniss, and tries to kill her upon their reunion in District 13.

The rebels take control of the districts and finally begin an assault on the Capitol itself, which Katniss is a part of. However, an assault on a "safe" Capitol neighborhood goes wrong, and Katniss and her team flee further into the Capitol with the intent of finding and killing President Snow. Eventually Katniss finds herself pressing on alone towards Snow's mansion, which has supposedly been opened to shelter Capitol children (but is actually intended to provide human shields for Snow). Afterwards, bombs placed in supply packages kill many of these children and a rebel medical team, including Katniss' sister Prim.

President Snow is tried and found guilty, but he tells Katniss that the final assault that killed Prim was ordered by President Coin, not the Capitol. Katniss realizes that if this is true, the bombing may have been the result of a plan originally developed by her friend Gale. Katniss realizes that she will never be able to look at Gale the same way, regardless of whether or not he was directly involved in Prim's death. Katniss remembers a conversation with Snow in which they promised not to lie to each other. When she is supposed to execute Snow, she realizes that he was telling the truth and kills Coin instead. A riot ensues and Snow is found dead, having possibly choked on his own blood or been trampled in the crowd. Katniss is acquitted due to her apparent insanity and returns to her home in District 12. Peeta returns soon after as well, having largely recovered from his brainwashing.

In the epilogue, Katniss speaks as an adult, more than fifteen years later. She is married to Peeta and they have two children. The Hunger Games are over, but she dreads the day her children learn the details of their parents' involvement in both the Games and the war. When she feels upset, Katniss has taken to reminding herself of every good thing that she has ever seen someone do.