Here you’ll find the bestsellers in nonfiction for the week according the big A’s website.
Note that you see Conspiracy of Fools: A True Story as well as The Fast Way to Write. These are the top two on Amazon and yet, are very different types of books. Third is another “true story” called The Informant. These probably read more like fiction but are based on true stories and can be listed in the non-fiction category, which is much less competitive than fiction, making it a wise choice for publishing in this fashion.
You can do the same thing, and who says the story has to be real? Try publishing in non-fiction to see what happens to your sales numbers. You can even use a fiction looking book cover design.