I once self published a book. Biggest mistake I made was writing it before i had an audience to sell to. I would take small snipets of your book and distribute for free to places where your target audience hangs out. Then publish more free bits on your site for email address. Maybe some complete short stories. Then once you have an audience that likes your shit promote a book to them, and leverage those sales as social proof to go more broad.

I will teach you to be rich does this really well. I don't have a good analogy for fiction but I'm sure they exist.