Four hundred years ago, Shakespeare showed us the fluidity of genre boundaries by writing plays that deliberately messed with Aristotle's definitions of tragedy and comedy. Compare Othello to Much Ado About Nothing, or take different scenes from Measure for Measure out of context, and you'll see what I mean.
Nonetheless, people persist in believing in genres, and in assigning different characteristics to them as if they were natural and even immutable. Sometimes it's something as silly as blanket attributions of quality (e.g., the ones we've seen over and over again, "It can't be science fiction; it's too good", or "Nobody ever wrote a romance as serious literature except Jane Austen", etc.). Sometimes it's an attempt to define different subgenres (e.g., Are time travel stories science fiction because they involve the logical consequences of a particular theory, or are they fantasy because they're impossible?). Sometimes it's a fight over which shelf the book will occupy in the bookstore (hence Margaret Atwood's insistence that her novels aren't SF, and people's perplexity as to whether The Time Traveler's Wife belongs with romance, literature or SF).I typically ignore genre definitions per se while writing first and second drafts, because they get in the way of whatever I'm trying to do with the story. Like many people, I see so-called "mainstream" fiction as a subset of the larger universe of fictive possibilities:
Of course, sometimes you'll deliberately mimic or parody a particular style that you tend to see more in one genre than another, and in such cases it helps to know the landscape in which such genres are written so that the reader will get the joke. But that's actually easier to do than you might think. (When Glen David Gold and I were in college, he wrote a parody of John Irving based on having read one book and seen one movie. Because Glen is an assiduous reader and a masterful writer, the parody was hilarious and dead-on-target even to those of us who were much more familiar with Irving's writing. You don't need deep familiarity with the "genre" as a whole.)But when you are speaking of intangible phenomena, belief and perception matter. I may be sure that genre is really an illusion or convention, but if my reader believes in it, then it's relevant. Nor is it relevant merely as a marketing tool; readers who are steeped in particular traditions will have different habits of thought, and this effects what your story will do for them.
I recently sent a short story draft out to two different sets of readers; it went to my gang of SFF writer-pals for the usual Clarion-style critique, and also to some visual artists because it took place in the art world, and I wanted to make sure I hadn't blown anything. The story employed a clueless narrator who was unaware of the fantasy element of the tale, and my compositional task was to make the reader see it even though the narrator didn't. My SFF friends said that I was beating the reader over the head with the hints, and that I could cut the story down by eliminating half of them. But some of my visual- artist friends didn't see the element at all.
How I proceed next on this story depends on who I expect the audience to be. If I'm going to sell it to F&SF or Fantasy Magazine, I'll cut it down as my Clarion buddies suggest, because they're a pretty good proxy for the target reader (and editor). But if I'm aiming at The Pedestal or The Newport Review, then I'll leave in the hints and maybe add even more.
It isn't that fantasy readers are smarter or better at figuring out hints; it's that figuring out what is not "here and now" about a story is something they assume they'll always have to do. This can backfire, too: I once used a hair metaphor to describe a character in an SF story; in order to show how the protagonist felt about her; because I did it early on, my first group of SFF readers thought she must be a gorilla or something. Had it been a "mainstream" audience, they'd know it was a metaphor from the get-go.
So while I get impatient with people trying to figure out whether The Time Traveler's Wife is science fiction, fantasy, romance or mainstream, I absolutely understand why it matters to them. A writer who aims a story at a romance audience, but has the lovers and their rivals die horrible deaths at the end, is making a clear literary statement; a writer who aims the exact same ending at a horror audience is making a statement too, but an entirely different one.
This is almost a cultural or religious difference -- it has to do with the different assumptions that underlie the thinking of different groups of people, the "map" on which they see the world. The fact that I don't usually think in terms of genre doesn't matter, because I know that my reader probably will, or at least will bring a different world-view to the matter.
And anyway, I'm being disingenuous when I say I don't think in terms of genre. I've plowed though more editions of Dozois's Year's Best Science Fiction than I can count; have I ever finished an entire edition of Best American Short Stories?
Obviously genre matters, at some level, even to me.
