Hunger Games, by Suzanne Collins
When Katniss' little sister is selected as a tribute to the Hunger Games, Katniss volunteers herself to compete in her place. She, along with Peeta Mellark, a boy who saved Katniss' life in the past, are transported off to the Capitol district in order to train in combat among other things in preparation to enter the showdown between the 24 tributes.
It is a suspenseful tale that delves into such things as morality in the face of desperation, and the consequences that are result of your actions.
Book 1 of 3. A great read.