Some advice: See it before 10 PM because it is LONG and you will get tired!
I thought it was good and stuck to the book fairly well. I understand everything that was going on because I had read the series, but I think I might not have appreciated it as much or fully got as much, if I hadn't read it.
The characters were ok. Good, not great, a bit bland. Lenny Kravitz and Stanley Tucci were pretty phenomenal though, I thought.
Definitely see it if you like the books! I can't wait for the next one.