The movie was a faithful adaptation to the novel (well, as faithful as a movie can be) with lots of added in bits that actually help to enhance the story (such as the behind scenes interactions between President Snow and Seneca Crane). The book is still better (as books usually) are but for the uninitiated the story should be easy to follow.
I understand that the movie had to tone down the violence in order to earn a PG-13 rating (and therefore be able to make money) but I do feel like some of the horrors are too toned down. Yes, the concept is disturbing and that's the point. The movie loses some of that but it's not a 100% dealbreaker for me.
Jennifer Lawrence is AMAZING. If nothing else, go see it for her amazing performance.
At first I was opposed to the 7th Harry Potter book being split into 2 movies but I soon realized that this was necessary. Every chapter counts in the novel in order to make the whole story make sense. If the filmmakers had not made a faithful adaptation, film viewers would have been thoroughly confused (which is what happened in a few of the previous movies). The filmmakers have really done justice to the novel and have managed to create the sense of urgency, dread, and despair that permeates the wizarding world. In some ways, they have even managed to enhance this feeling of doom (more than the novel could). That being said, if you haven't seen the previous movies or read any of the books, this is not the movie for you.