Society collapsed in North America after a nuclear war. A new society called Pan-em arose. Pan-em is a dictatorship centered around the Capitol, and there are 13 districts of extreme poverty that serve this single city as its labor castes (i.e. one produces lumber, one produces food, the main character is from the coal mining community, etc).
74 (?) years before the books start, the districts rebelled. The Capitol eventually regained control by eradicating District 13 off the map. In order to prevent rebellion in the future, harsher curfews and food shortages were enforced on each district, and the Hunger Games were invented.
The Hunger Games take place every year and operate as "a reminder to the lives lost in the rebellion." It takes the form Battle Royale meets reality TV. Every child between the ages of 10 and 16 is eligible to play if they sign up for lots in the taesarae, which is a lottery where a family gets extra rations of grain for every time their kid signs up. Each district sends one female and one male to the capitol.
At the Capitol, they are required to train in a weapon and outdoor survival techniques. They participate in a fashion show and TV interview. Then all 24 kids are transported to an Arena and forced to fight to the death.
In the center of the Arena is a massive pile of weapons where the best stuff is in the very middle, so there is usually a massacre as the most ruthless kids try to get the best weapons. It is surrounded on all sides by a massive wooded area (usually) that is mined with every futuristic death trap imaginable. Lasers, genetically engineered swarms of smart animals, artificial volcanos, etc.
The best part (to me, at least) is the gifts. The audience in the Capitol can pay money online to have weapons, medicine, or food dropped into their favorite players. But since the Capitol is full of heartless, decadent fools, they will only help those who most entertain them. So as they are murdering each other, the kids are manufacturing alliances, romances, rivalries, and anything else they feel will please the viewers, all just so they can get some medicine to stop their hallucinogenic wasp stings or whatever.
Anyway, that's all in the first book. The second focuses on the main character having to go back to the game and third starts a new rebellion against the Capitol. It think its insanely gamable because you could use the different skill sets of each district as classes. You would also have the option of making it largely a PVP game by running one of the Hunger Games, or you could set up a campaign in the rebellion-mode. There are all sorts of crazy monsters, jackbooted thugs, and devious traps to throw PC's up against either way.
