In the course of her analysis of The Lord of The Rings, Christine Brooke-Rose draws a distinction between realist and science fiction narratives whereby the former maximizes familiarity: ‘the realist narrative is hitched to a megastory (history, geography), itself valorised, which doubles and illuminates it, creating expectations on the line of least resistance through a text already known, usually as close as possible to the reader's experience’. By contrast, ‘in the marvellous, there is usually no such megatext, at most a vague setting (Baghdad, a city, a village), in no specified time. Sf usually creates a fictional historico-geographico-sociological megatext but leaves it relatively vague, concentrating on technical marvels.’ So works like Dombey and Son and A Portrait of the Artist as a Young Man would be read within framing grand narratives of the history of railway expansion or of Irish Catholicism; but Brooke-Rose dismisses the corresponding ‘megastory’ for science fiction rather too easily. Wells's War of the Worlds, for instance, is packed with descriptive data testifying to Britain's military prowess and economic prosperity, a historical moment against which a different grand narrative—that of evolution—can pull through the means of the invasion story. Or, to take a more recent example, Octavia Butler's Parable of the Sower draws on a whole history of inner-city neglect and ethnic tensions to set up its narrative. In many science fiction novels the realist megastory is neither ignored nor replaced, but selectively installed.

Brooke-Rose problematically links The Lord of the Rings to science fiction through the specific case of a mega-narrative which the author cannot assume is already known by readers and which therefore has to be explained at greater length than in realist fiction; and here the appropriate works for comparison would be not science fiction in general but those sequences of novels and short stories which place themselves within an epic frame. Patrick Parrinder has argued that much science fiction can be read as ‘truncated epic’ because in dealing with future or alternative history there is often a disparity between subject and narration: ‘If the events that they portray are of epic magnitude, the manner of their portrayal is brief and allegorical, reminiscent not of the poem in twelve books but of the traditional fable.’