My two biggest criticisms are one, they writers of the movie added a lot more corny love stuff and two, most of the violence is implied and not shown. The second criticism I can understand. When someone's making a movie based on a brutal, violent book it's going to be rated R. The fact is though that most people reading the Hunger Games books don't go to rated R movies. So, the writers cut out large chunks of violence and replaced it with sappy love bull-crap.
Besides those two things the movie was a pretty good representation of the book. The book is still better, though.
When the first hunger games book came out I was in 3rd grade and most kids weren't into it much. It wasn't until my year of 5th grade that I saw a lot more interest in the series. Most of my friends totally lost interest in the books in 6th grade (that I know of) and when the movie came out more kids started reading the book. So...the movie was a good, three star, representation of the book.