Fiction is supposed to read in a similar way to how a movie plays. A cinematographer and their ilk intend to construct scenes for viewers to see on a screen, much akin to an author using words to convey a particular image which the reader ascertains through reading. However, there is a discrepancy in relation to the image of the film and the image of the novel. Consider the following fictional scenario: a green alien breaks into a donut shop in which he steals coffee and donuts. For the film-makers, they are going to use real props, or perhaps CGI, or even both, to portray this. Maybe they will make the alien bright green, have donuts with pink frosting and sprinkles, black coffee, a 1990s checkered floor, a neon "closed" sign, etc. There is only going to be one scene for this film and that will be the scene on the screen. Now, perhaps an author will go into great detail and try to make it as objective as possible, but there will be no external alien, nor will there be donuts, nor a "closed" sign, and so forth, to see. The reader has to conjure up the scenery in their own head. In a sense, "there is nothing outside of the text," to use that mistranslated quotation from Derrida.
But that's not the entire story. This lack of need for an imagination can be extended to non-fiction, as well. Suppose that I am interested in statistics, and I want to learn about cigarette smoking in a given area. So, I decide to go online and read about it. I might have images of people of different ages in my head, say, if I am comparing cigarette use based on age. But such images do not truly matter like they would in a work of fiction because statistics are about cold facts and not a creative story. The mental labor that comes with reading statistics is mere scribbling in the margins compared to the Picasso-attempts that come with reading fiction. Fiction is two-fold in its ontology. There is the ontology of the text itself and the ontology of the imagination of the reader. The former is objective while the latter is subjective. There is no such complex of ontology that comes with non-fiction or films.