I have recently had the pleasure of writing an article for Bob Martin's brand-new Web Earner website. Not surprisingly for people who follow what I write, you will discover that I talk about books, but the greater emphasis is on how to have a successful, web-based business. It is very difficult to subsist on one or two books.
However, if it is a non-fiction book, there is likely a website in there somewhere. For me, it was about online high schools. For you, it is likely something else. Whatever it may be, find that connection and you are much closer to having a viable business publishing books.
Also, I would encourage you to go over to the article, Internet Business for the Masses, and have a read.