It can be so hard to "find your niche", whether it's on the bookshelves, or in the other parts of Real Life. Apparently we humans can only cope with stuff if we can categorize it. The problem is that very few things fit in only ONE category, but it's as if the rule book says, "One category per customer". So we struggle to find that one perfect descriptor, the mot juste that will let all the people searching sigh with relief once they've found this particular item.
But how can you find your niche if it hasn't been created yet? When it comes to publishing, there are certain pre-set categories/niches that authors are asked to squeeze their manuscript into. The funny thing is, the more somebody tries to make something fit, the more that category expands, to the point that the original description doesn't begin to cover it anymore.
I'm assuming back in the days when storytelling was oral, not written, there were no categories. It was a "story", something to pass the time while gnawing on brontosaurus bones, as well as a way to applaud the bravery of the brontosaurus catcher, and inspire future brontosaurus hunters to great deeds.
No doubt the stories changed with the re-telling, for any number of reasons. Maybe Gork was in a hurry to see Mrs. Gork one night, and abbreviated certain parts so he could get to "The End" more quickly. Or maybe Gork Junior was yawning during the fifteenth re-telling, so Gork revised based on the immediate audience feedback. Or perhaps there was a Gork wannabe, who was transcribing the tale by drawing stick figures on the cave walls, and he decided to tell the story from the brontosaurus point-of-view.
From that point it seems there was "fiction" and "non-fiction", and that probably sufficed for a while. But then sub-categories started cropping up, so it was necessary to re-organize, so that people could find what they were looking for again. And then the sub-categories started to expand.
For instance, the category of "romance" was too big to cover all the myriad variations of stories. "Contemporary" and "historical" made things easier, but then how do you deal with things like vampires and werewolves? Um, let's create "paranormal". But what about when these paranormal stories focus less on the romance? Well, we can call it "urban fantasy".
Writers keep writing the stories they love, and then try to find the appropriate slot on the bookshelf. Too often they're told "I don't know how to sell this", which means, "there isn't a category that fits this yet".
The only thing you can do is create your own category. (Granted, we all want to be labeled "best-selling", but that's another post.) Instead of trying to mold yourself to fit into the current niches, which will often result in losing your voice, or hook, or the storyline that makes your book wow everyone who reads it – what you need to do is create your own category.
Sounds hard though. How do you pitch a book, to an agent or an editor, when it doesn't fit in the pre-defined categories? You describe the story, the elements that make everyone want to know: "what happens next?" You make everyone care about the characters, and what they're striving for, whether it's set on the desolate fourteenth moon of Jupiter, in the fiery cubicle of Satan's business manager, or a Mississippi riverboat piloted by prom queens.
Every time I've heard a writer ask an agent/editor panel, "Would you consider such-and-such story" (generally a story without a current category), the agent/editor replies, "I'm looking for a great story".
Your story is great. It may not fit into a particular slot on the current bookshelves. If it doesn't, that's fine, because now your job is changing "That's not what we're looking for", into "Because we didn't know we were looking for THIS!"