While photography is pretty singularly a visual medium and books are a medium very much completely reliant on the words - film is an art form that spans mediums. The words are just as important a component to the success of a film (I mean artistic success - not commercial) as is how the film looks and what it does visually, both large and small (people who talk about film tend to sometimes forget that a low-budget film, or one that forgoes large sets and special effects, is still making a visual statement).