Where would we be without genre labels? Free to write new and weird idioms, possibly. But a couple of recent blog posts make the case that genres aren't cages, they're toolkits that tell you how to read a particular text.
The io9 article links in turn to Jo Walton at Tor.com, who says:
Science fiction may be literalization of metaphor, it may be open to metaphorical, symbolic and even allegorical readings, but what’s real within the story is real within the story, or there’s no there there.
The summary article also quotes Rachel Swirsky at Jeff Vandemeer's blog:
Genre distinctions aren't useless - they are ways of signaling expectations to readers, and establishing reading conventions... I think the problem comes when we start reifying genre and assuming that the barriers between genres are somehow real and important barriers, rather than being useful human constructions that can be argued over and negotiated.
Writes another contributor to the latter, A.D. Jameson:
I love genre, because genres are basically conventions. They’re expectations that both authors and readers (and editors, and sales people) bring to a text—suggestions as to what should be inside, and how it should be arranged. And I dearly love conventions, because they’re the very stuff of communication, and of artistic structure—whether we’re obeying them, or departing from them.
Read the summary article containing links to all the above here. Also includes mention of zombies, fantasy and a whole lot of other books I don't personally like to read. What I do like about this discussion is that you don't hear it (enough) in literary circles. It's sincere and straight up.