Many authors have it easy. They write in a distinct style and genre, which makes publishing houses happy. Stephen King's stuff gets stuck in with the horror (usually), James Patterson's stuff gets stuck with mystery (usually), and so forth. Even genre indie authors who are self-publishing frequently don't have to ask how to define their books and stories because, hey, it's a romance/science fiction/horror/urban fantasy/whatever book, so we put it in those sections.
When there's cross-genre writers like me.
By its very nature, cross-genre fiction straddles or blends two or more genres and makes something new out of it--a twist on a conventional genre, or an outright subversion of the tropes that come with it due to the nature of the extra-genre twist. They're often hard as hell to fit in any on particular box, and usually that's how I like it.
I learned about this problem when I was getting the Amazon information entered for Sheep's Clothing, my Weird Western featuring vampire hunting in the Territories in 1874. Weird Western is an actual thing (as in, an industry-recognized genre combining Western elements with speculative fiction), so I didn't think I would have any problems.
When I got to the BISAC subject heading. See, there's a list of possible book subjects compiled by the Book Industry Study Group to standardize the sharing of book subject information. The choices it offered me were Fiction/Horror or Fiction/Westerns. There was no Fiction/Weird Western category. On one level I understand, because Weird Western isn't exactly mainstream, but if the publishing industry recognizes it, why not the BISG?
I can only expect this will continue to plague my work as I get more into the self-pub stuff because, just to take a cross-section of my works-in-progress and unpublished stuff, there is no category for Fiction/Science Fiction/Romance, nor is there a category for Fiction/Fantasy/Mystery or Fiction/Mystery & Detective/Fantasy, or Fiction/Fantasy/Spy Thriller. And I don't think I'm going to see Fiction/Chick Lit/Paranormal anytime soon.
So what is a cross-genre author to do with such limitations? For the time being, I suppose we can work within the limitations of BISAC for the sake of making the entry form happy, because it wasn't going to let me NOT categorize my novel, not was there a "none of the above" option. (Fiction/General totally doesn't count.) And of course, once my novel is out there in the reading world, I can market it however I like and zero in on the Weird Western crowd that way.
(I wound up categorizing Sheep's Clothing as Fiction/Westerns, by the way.)