Why write a niche book?
Writers tend to think first about just writing a book. Most of them don't think about marketability and business. If they do think about it, they don't consider the broader demographics and factors. When you write in a niche genre, for example, it's already going to have a narrow audience. A narrow audience though is relative when it comes to sales. What does this mean? A narrow audience is like a narrow river. You have about "this much opportunity" in that space. It flows and people come in and out (your audience and customers). You probably don't have that much competition in that space, because it's not a common theme or idea you're writing about. You do want to attract people from the narrow audience to your book. Because you don't have much competition than your book might be one of a handful or the ONLY one on the bookshelf to select. If you're one of a few, your chances of capturing those few buyers goes way up. So fewer consumers...