Thanks for this. I realize I am asking you to do my homework, at least a bit. Learning new stuff is difficult these days. You'll understand that in time, with a bit of luck.
My real concern is with epub. Some things don't convert well to mobi or azw3 but most do. Lately I'm reading epub on my phone most of the time though.
In CSS how do I know which is the chapter block style? I did try changing references to different CSS styles but that didn't seem to affect anything at all. However those changes were made in the book. I didn't try changing anything in the CSS.
Barry