Authors and Movie Adaptations of their Novels

The film industry has been adapting novels to the big screen for many years. Most of these movies become big successes in the industry but surprisingly some of the best movies have been disliked by the authors who wrote the original idea. Most of the reasons why the authors dislike the film adaptations of their novels is because the director may tend to leave some things out of the book or not follow the story exactly as it was written. The author of Mary Poppins, P.L. Travers, had some heated debates with the producers as his script edits were mostly disregarded. Steven King had said he was largely disappointed with Kubrick's The Shining because he didn't like Jack Nicholson's performance and also because Kubrick couldn't grasp the concept of the evil of the Overlook Hotel. Because the producers of Forrest Gump omitted plot points and downplayed sex and violence in the movie, The author, Winston Groom, started his sequel with the lines "don't ever let anyone make a movie of your life story". Even the author of The Clockwork Orange regretted writing the book in the first place because the movie made it seem it was all about sex and violence.
These are all movies that have become hits in the film industry. It is hard for me to decide whether the authors or the producers are the right ones with the right decisions in the movie making process. Although I see how most film adaptations aren't completely "puritan" to the novels, they end up becoming hits and become some of the most beloved films in our society.