I read The Hobbit before LOTR: The Fellowship of the Ring came out. As I was watching the Fellowship, I was startled by how scary the orcs looked. We both read similar source material. Where did they pull their version of what an orc looks like, and where did I pull mine? It was my first concrete experience with someone else's version of the same material. It was also my first experience realizing my mind wants to protect me from scary images. This may be part of the reason I have a difficult time with horror movies - it is someone else's scary vision, which is a billion times scarier than my mind would allow.
When you read a book, you interpret it in your own way. You bring your past experiences, biases, and opinions to the table. You can't read a book free of these things. Part of what makes a book club so fun is hearing other people's interpretations. I have yet to walk away from a discussion feeling unfulfilled, even when I didn't enjoy the book.
The problem with a movie is it narrows this experience to one vision. When I see an orc, I am getting the designer's version of what the orc looks like. It may look similar to mine, it may not, but the problem is I'm only getting one person's version. And for most people, who don't read books, that is the only version they're getting. They make their own interpretations off of an interpretation. It's a copy of a copy. They don't get the chance to make their own versions of what the characters and settings look like, since someone else has already put the images into their heads. They lose this beautiful step.
Howl's Movie Castle: a book AND a movie I love!
Movies are their own special medium for telling stories. Why aren't there more original scripts for movies? People often write new plays, which is similar to a movie, at least more similar than a book. You will always lose something when you adapt a book into a movie. Writing an original script for a movie allows the story to be told fully, since it is told in the intended style.
I know sharing this opinion makes me sound like a movie-hater, which I'm not. I just think we rely too heavily on books as source material for movies, when movies could be so much more.