This book is really awesome - I read it in a single day (two sittings). Loved it!
It takes place in a dystopian future (yay, dystopia!), in Panem, which was built on the ruins of North America. One city, the Capitol (set in the Rockies) rules over the twelve remaining Districts - and every year, to remind them of its dominance, it requires two tributes, a boy and a girl between the ages of 12 and 18, who will compete in the Hunger Games.
These games are televised, and it is mandatory for everyone to watch them - to watch as the tributes fight the environment of the arena, as they fight the traps that the game masters have put to make everything more exciting, and as they fight each other. Of the 24 tributes, only one will survive, and they'll have a life of luxury and fame afterwards.
Now, our protagonist, Katniss, is a sixteen-year-old from the poorer part of District 12; and when her twelve-year-old sister (who she loves very much) is picked as the district's tribune, she takes her (the sister's) place and must compete in the very lethal Hunger Games. There's also a love interest somewhere; it's not very subtle, but it's there. You'll see.
The writing was excellent, really; some scenes felt as though I was seeing an action movie rather than reading a book, and now I just can't wait to read the sequel.