alt Hacker NewsI've written over a dozen books.
Have used asciidoc, HTML, word, latex, and rst.
Markdown is the least painful of all. It's not perfect but the others are worse.
(My custom stack uses markdown (or Jupyter notebooks converted to markdown). Pandoc plus some custom filters creates typst (for PDF) or epub.)
I did a book in rst and liked that it had cool admonition, import, glossary, and index features that made it better than markdown for me. Still hate the heading conventions.