I think there is a lot in the movie that didn't happen in the book (it was years ago read it but i think i'm right) i suppose they needed to pad it out to make three very long movies the book is quite short i remember, the normal 3d was great, we were going to go see the high definition 3d but read mixed reviews on that ranging from "great" to "it looks like 1970's home movie footage" but as i said the normal 3d was great nearly up to Avatar standards, i was bit worried after watching really poor 3d in Prometheus, also i read reviews the movie was too long and a bit boring, there was much more action in this first one then there was in The Lord of the Rings first movie.
Yup, just got back from watching it, i loved it, Peter Jackson strikes again with the breathtaking sceanery, Id did vary in spots from the book... the scene with the 3 trolls was totaly different in the book. They didnt vary too far on things to totaly remake it, i still loved it and look forward for the next one!