Catching Fire (Hunger Games, Book 2) by Suzanne Collins

After winning the brutal Hunger Games, Katniss Everdeen returns to her district, hoping for a peaceful future. But Katniss starts to hear rumours of a deadly rebellion against the Capitol. A rebellion that she and Peeta have helped to create. As Katniss and Peeta are forced to visit the districts on the Capitol's cruel Victory Tour, the stakes are higher than ever. Unless Katniss and Peeta can convince the world that they are still lost in their love for each other, the consequences will be horrifying. The terrifying sequel to The Hunger Games.