Almost 15 years ago or maybe more, I read the "Fellowship of the Ring" in the Spanish translation, still being and adolescent. Some years later I saw the movie which was as good as I expected it to be, but I never thought too much about the many differences between the book and the movie adaptation believing it was more or less a straightforward adaptation with some minor changes.
After reading a lot of other Middle-Earth related books and stories, I set to read the Lord of the Rings saga once again in its original language. This was something I wanted to do a long time ago, but it was partially promoted by the movie adaptation of "The Hobbit" where I realized many details int he story I did not realize when I read it back in 1998.
To my surprise, after finishing the Fellowship of the Ring I have to say that the movie is an awesome adaptation. Even more, I would even dare to say that it's a better work than book. A real derivative work.
One could argue that the movie is visually more appealing and stunning, that the rhythm is paced more accordingly to modern times, and that the actions scenes are much more vivid. And I don't deny all of that, but those are not the reasons I think the movie is better than the book.
I'll not detail every change or omission in the movie, because I don't remember every detail from it and it can be reliably read here. Noteworthy omission is Tom Bombadill, which I did not miss at all!
There are two strong changes: one is the role of Arwen, and the second the Council and the subsequent formation of the Fellowship. These changes make the movie much better in my opinion.
Regarding Arwen, in the book she barely gets mentioned like two times and only the second exploring the tension/relation between her and Aragorn. In the movie this is made very explicit in many scenes in particular when they meet during the Council. This change could be motivated to make the story more appealing to a wider audience and as such maybe with a market reason behind. In any case, I think that this change makes the movie stronger and interesting and the book was very lacking in interpersonal relationships.
The whole Council scene is dramatically changed. Where in the book the fellowship is mostly decided by Elrond as he deemed fit, in the movie the different characters volunteered on their own will to be part of the fellowship. This free will decision, is a very important element turning the scene into a powerful and moving one for me, and I really missed it in the book.
Now I'm really looking forward to see once again the movies once I finish the rest of the saga, to keep comparing changes in emphasis and of course to enjoy the story once again in an extended version.