Adapting a novel to the screen takes time, skill and the ability to retain the vision of the original story into the confines of 120 pages or less of a screenplay, which is mostly dialogue and very short descriptions of scenes, action and shots. The screenwriter must love the story and be able to take the most visual and story-rich parts of the novel and craft them into the film so the viewer still feels the author's original intent. Done well, the film feels true to the novel.