You might check out a well-done series of posts on self-publishing by Doug Farren. Doug was part of my Launch Pad Astronomy workshop class of 2013. He has had a good deal of success self-publishing, and while self-publishing is not my particular cup of tea¹, I’ve found Doug’s posts on the subject both enjoyable and enlightening. If you have any interest whatsoever in self-publishing, go check out his posts on the subject.