I used Asciidoctor. It's mostly the default theme, but I tweaked a few things about it.

If you're interested in the details, I wrote a blog post that goes into it a bit more: https://www.kevinwmcconnell.com/writing/how-i-wrote-my-book

That post also has a link to a repo with all the settings/theme/etc, so anyone can take it and use it as a starting point for their own book.

In the article, you reference `asciidoctor-epub`—I think you mean `asciidoctor-epub3`? Might be worth updating or correcting me here.

Ah yes, you're right! Thanks, I'll fix that.

Thanks!