The Hunger Games depicts a dystopian future in the very wealthy nation of Panem, which has 12 much poorer districts. Brought on by past indiscretions by the districts they must over up children ages 12 - 18 to take part in a lottery. The "winner", one male and one female, then take part in a televised competition, until only one is left alive. Our protagonist's sister is selected, and Katniss selflessly offers herself up on the sacrificial pit instead. Katniss is teamed with the male chosen from her district, Peeta, someone with whom she knows all to well already.
Rather than talk about the allegories to different classes alluded to in the film, which quite frankly are general enough that you could cast any set of characters in their roles. I'd rather skip that and go right into the film itself. Quite frankly, if you're going in as someone who has not read the books - this film does a piss poor job of explaining why things are happening. Just fill in whatever back story you want is the films motto. You know immediately from the start to not invest anytime with any characters since there's a great deal of chance they will be dead. The only real character development we have occurs before the "lottery" even takes place.
It's such a glossy, sanitized version of the book, that it may as well be laminated. The director never lets us get interested in the film itself. Every chance we start to get intrigued by what's going on, it's over. The entire film is a pair of work khakis. To make up for the fact that the movie is the most abrupt 2 hour movie I have come across. To make up for the fact that there isn't any depth to this version of The Hunger Games, Ross shakes the camera uncontrollably, at all times. I was almost certain I was drunk, I was seeing double so often.
So, Cronos, if all you have to say is bad thing about it - how is it a 3.5? Even with the story being butchered, neutered, and spiceless - the story is just that good. It's fantastic, and has every level of suspense you could want. Even removing most of that suspense (possibly all), it's still enough to make this a good movie.
On top of that, the acting is superb, from the entire cast. Most especially from Jennifer Lawrence. This is all from her POV, she is the spotlight and the wheel that makes this unicycle run. She is fantastic in every scene and despite the directors bests efforts to the contrary, her acting alone kept sucking me into the story. No matter how shallow and tepid the water was, I couldn't help it.
Read the book, see the movie. But seriously, read the book.