Obviously, one main reason it is extremely difficult to turn a book into a movie is because of the human mind. When reading, our own creativity and imagination takes over, so we build on what the author writes without even realizing it. In a way, each reader creates a different world in their own mind, so no one can be completely satisfied with a movie, because it gives the directors vision which may be different from our own.
However, I think some interpretations go beyond this, and many movies just stray so far from the book that they become an entirely new project. Most often, this occurs when directors and writers change the plot of the book to fit hollywood standards.
Take one of my favorite paranormal romances Blood and Chocolate for example. The takeaway message of the book is that sometimes you need to stick with your own kind and the people that understand you. However, that is not a popular message in Hollywood, so they completely changed the storyline to make it seem as though fighting the odds is what is important. The book was so amazing because of the unique message, and the movie completely transformed that and changed the entire storyline. I enjoyed the movie, but view it as a completely different story, because the adaptation was just horrendous and all of the characters were changed.
But sometimes, it's not the total change of the plot that bothers me, but what is omitted. While a book can have romance and action and mystery and psychology all in one, movies often times have to fit into a very specified genre, like an 'action' film or a 'romantic comedy.' Even if the movie does not need to be changed, directors will often highlight one aspect like the romance or the action to make it more marketable. This is the change I am most worried about with The Hunger Games, because most of the press releases have thus far seemed to focus on the love triangle, which really isn't the focus of the books. However, I think they might change the movie to make it more about love and less about the nature of dystopian societies and war.
Finally, sometimes it is not even big changes that bother me, but the little ones that would be so easy to keep accurate. Anyone who has been following news on The Hunger Games movie knows that the color of the backpack isn't bright orange like in the books. Such a small detail won't make or break the movie for me, but I just don't understand why a director would change something that is so simple to keep true to the novel.
Some of the movies that I think had the worst adaptations are: Da Vinci Code, Ella Enchanted, The Lovely Bones and Shopaholic.
What movies do you think were the worst? Why? What about the best? I personally loved the Harry Potter films.
I'd love to hear what you think! And here's The Hunger Games trailer in case you haven't seen it yet.