I had no idea what it was until two weeks ago, around the time people started frothing with excitement and talking about it everywhere.
I saw the movie last night. It was... ok. Yeah, it's targeting the younger crowed, the PG13 rating certainly dragged it down. I thought was struggling to maintain the seriousness and savagery of the "games" with that rating. The dialogue was tolerable, the cast was ok, save for Jennifer Lawrence; she was great, and definitely carried the movie.
I'm not good with rating movies, but I can easily dock the experience a star or two for how horrible all the hyperactive children and manchildren were at the theater. If you're sensitive to those crowds, you better avoid it for now.