I had a long disagreement yesterday about the definition of genre.* It began with my contention that all fiction is genre fiction, even if literary fiction readers are loathe to admit it. My worthy opponent not only rejected this broadening of the tendency to categorize fiction, but my use of the word "genre" in this sense, period. He seems to think that genre, as the term is used by the average person, does not signify the content of a literary work (in that certain tropes, themes, stock plots/characters are present) but instead refers to works which are consumed by people who interact with the works and each other in specific ways.
This definition enables one to define science fiction and fantasy as genres, but to exclude romance and horror, despite the frequent descriptions of those categories of books as "genre." It alsolets you say that works like Oryx and Crake, which appropriates the themes of SF to explore some of the same issues as have many previous SF writers, are not genre, while a work lacking any thematic connection to SF (and which might have the content marking of what I would call a completely different genre) would be genre SF if the SF fan community interacted with the work in the same way as it would with an SF work.
To me, this sounds like a great lot of rubbish. Can I get an amen? "Genre" fiction at least includes the traditional ghettos of mystery, SF, fantasy, horror, and westerns. It should include the emerging categories within lit fic as well; who can argue that narcissistic Boomer memoirs from the 1960s do not now constitute their own genre? Basing the categorization of a book the identity of its readers is profoundly unscientific, indeterminable for unpublished works, and just plain silly.
Readers may be interested in this NY Times article on SF. It features a quotation from Mary Doria Russell, author of the excellent novel The Sparrow.
* genre: A particular style or category of works of art; esp. a type of literary work characterized by a particular form, style, or purpose. (OED 2d ed. 1989)