The structuralist critic Tzvetan Todorov articulated the fantastic as a literary subgenre in the mid-20th century. The fantastic defines a subset of works generally classified within the genres of fantasy or horror, mostly written between the mid-19th and mid-20th centuries.
In works that are fantastic, supernatural forces are presented ambiguously so that the reader is unsure whether to attribute circumstances in the book to truly supernatural happenings (in which case the story moves into the marvelous) or to normal but perhaps unusual occurrences of reality (in which case the story moves into the uncanny). The fantastic is maintained as long as the reader is kept wavering between these two extremes, and a fantastic story is one that maintains this fantastic effect for some or the entire story.
Hoffmann's The Sandman (as well as some of his other stories such as The Golden Flower Pot and The Nutcracker and the King of Mice) is a classic example of the fantastic due to the ambiguity of reality and the coloring of the narrative by Nathanael's fits of madness. The tale could be classified as uncanny if it was decided that Nathanael hallucinated or misperceived the entire story, from childhood to adulthood; however, from the narrator's vantage it seems as though there is some reality of Coppelius attempting to steal and examine eyes and re-emerging later in Nathanael's life as Coppola.
Sigmund Freud further investigated the fantastic in his 1919 essay "The Uncanny." Freud's belief was that the feeling experienced by the reader while reading a fantastic work comes from the mix of heimlich (homelike, familiar) and unheimlich (un-homelike, unfamiliar). Freud used Hoffmann's The Sandman to analyze and support this theory.
Other classic examples of the literary fantastic are Algernon Blackwell's The Willows, Nikolai Gogol's The Nose, Guy de Maupassant's The Horla, and many of Edgar Allan Poe's short works. Thomas Trezise, a scholar and professor of literature at Princeton University, argues that even works as recent as Toni Morrison's Beloved might be included as modern examples of the genre.