Writer Kristine Kathryn Rusch talks about tie-in writing and the publishing biz in an interesting interview with SciFi.com. Along the way, she had this to say about self-publishing:
Vanity presses are called "vanity" presses for a reason. They appeal
to the writer’s vanity, not the writer’s sanity. Stay away if you want
to be a serious writer.
Good advice!
It is. I would never do it again, or have done it in the first place in retrospect, specialized nonfiction or not.