If you read the books, you are fine. If not, don't waste your time. I love the series and the characters - so it was enjoyable to watch them develop into young adults, etc. If you are not invested in the series, this movie would leave you wondering what was going on.
I loved the movie (have seen it twice). It's missing some of the most emotion-filled intense feeling parts of the book. It has beautiful imagery and some parts made the audience laugh out loud. Can't wait to see what they do with Part 2.