Nearly all good films build around engaging stories with memorable characters. Thus, Hollywood and Independent filmmakers have often turned to novels for raw material. With a novel, you at least know that you start with something that works. But, the novel is just a starting place – for as certainly as a great novel like A Tree Grows in Brooklyn can be made into a great film, so certainly can a great novel like Dune become a dreadful film.
Among the many problems of adaptation, chief may be that in the novel an author can speak a character’s mind, whereas in a film, apart from an occasional, and risky, voice-over, thoughts must be visualized. Remarkable how many great novels depend in key moments on the interior worlds of certain characters – think of any Russian novel, for example, like Dostoievski’s Crime and Punishment . The tormented protagonist can’t tell us he is tormented in a film version. We can’t read his thoughts. He must look and act tormented, and that can be difficult to pull off without maudlin performances or heavy-handed direction.
Then, comes the problem of length and pacing. A good film will have perhaps six key scenes. The script will build toward and pull away from these. A four-hundred-page novel may have a dozen or more key scenes, or it may unfold gradually without huge peaks – think of a Willa Cather novel, for instance. What was wrong with The Return of the King, Peter Jackson’s concluding segment of The Lord of the Rings? Well, he strained a couple scenes, like the joyous return around Frodo’s bed and the departure to the Far Havens, to fit the conventions of filmmaking and thus threw the tone of the novel off-balance. And, he omitted one of the most thematically important scenes in the novel, the scouring of the Shire, so as not to throw the tone of the film off balance. A screenwriter has many difficult choices to make to boil a novel down to filmable size, choices that will guarantee enemies among the devotees of the book, and choices that pretty much guarantee a different texture to the final product.
Third, a novel tends to have far more characters than a film can allow. Often a screenwriter will combine several characters from a novel into one in the film, and then out of that process will emerge something much larger than was contained in the book. Remember that a character in a film can visually dominate once on screen. The character of Seymour in Ghost World, literally took over the film once created out of the bits of him you find in the graphic novel, especially as realized by actor Steve Buscemi. The result, as in most adaptations, is a new product altogether.