Thank you very much for your comment, though. It means a lot.
You give me a feeling you really care about the craft and just making a good useful resource, which what I respect. I looked around the site and bookmarked it as a technical writing example I might go to read around now and then.
I sometimes teach coding or general computing things (but hands-on, less about writing) and I've come to appreciate that sometimes it is extraordinarily difficult to educate on or communicate complicated ideas.
Quoting you: To give you a sense of what I mean by improving the book “over and over“, keep in mind that between feedback from my DE, external reviewers, and others, there are parts of the book that I rewrote more than ten times.
I also do rewriting especially with content I intend to be a resource or education piece. Obsessively rewrite. Make it shorter. Clearer. Oops that reads like crap let's start over. IMO having an urge to do this and address all feedback or your own itches means you care about your work. Just have to remind myself that that perfect is the enemy of good enough (or something like that I forgot if the expression went exactly like that).