on Live Write Thrive:
Amazon has many categories and subcategories for fiction, and if you upload your book into the Kindle store and choose general categories, you’re going to be competing with hundreds of thousands of books.
What you want for best discoverability is to have your book in categories that sell well yet don’t have tremendous competition.
All novels can fit in a multitude of subgenres, which we’ll see in just a moment. So while you might have in mind to write fantasy or mystery, which are popular genres that sell well, notching down to a couple of smaller niche genres will help your book have a better chance of coming up high in the search engines.
You need to be willing to adjust the type of novel you write or want to write. You may already be writing in a popular genre, such as romance. But this objective of finding a niche subgenre might mean you have to consider writing something a bit different from what you currently write or want to write. It may mean choosing an entirely different genre altogether.
What’s most important when considering a genre to write in is this: You should feel competent or comfortable with the thought of writing in that genre.