Consider an author’s roll in the writing of the screenplay if his novel is offered a film deal. Should the author be the main screenwriter? Should he be involved at all? Not everything in a book translates well to screen (which explains material that is only in the film & not the book). Not all authors are meant to be screenwriters (and not all screenwriters should be authors). So: do we segregate the two, or can they play nicely together?
I think the Harry Potter movies are a testament to authors and screenwriters working well together. J.K Rowling did not dominate decisions for the movies but she had great influence and insight, I've read that she greatly helped actors fill their role better by being there to give them deeper insight and background into the character. The actor of Snape knew his entire backstory long before anyone else because Rowling let him in on the secrets. The author should at least be well informed if the adaptations want to stick true to the books so they don't do anything that would contradict what might happen later in an unpublished series' next book. That being said it's okay to continue without author's influence if the adaptation makes clear to fans that it is blatantly deviating from the books such as with Game of Thrones now that it's caught up with the books and wants to continue production on their own terms, and spin offs like Full Metal Alchemist which animated itself before the manga concluded which led to drastically different endings (noticeable to those who didn't read the manga because the series was re-animated in FMA Brotherhood which stuck to the manga once it was done). – Slaidey9 years ago
Not to mention that J.K. Rowling is going to pen the movie Fantastic Beasts and Where to Find Them which takes place in the Wizarding World based on a book she wrote by the same name. Another note is that Suzanne Collins, author of The Hunger Games, actually started out as a script writer. The books are divided into a certain number of chapters that can be divided by three because she's so used to writing plays with three acts. Now those books are movies. I don't know how involved she was with the actual films, though. – VelvetRose9 years ago