I never finished the book, but I thought the film was pretty okay. I heard the author was a screenwriter first, so maybe her writing is best-suited for the screen rather than books? (I couldn't get into the book, and I love reading.)
There was some technical stuff that wasn't great, but the overall affect was good, I thought - although the whole Rue thing seemed kind of thrown in (apparently it seems like that in the book too). I did think the violence was handled very well and made quite realistic without much gore. The acting was pretty good too for a lot of it.