AbdulAlhazred
Legend
I actually wrote my own 'meta markup language' for my stuff, but I'm sure not everyone will go that far, lol. Markdown is OK, but far too simple for book length projects that need nice layout.I found GitHub Pages a really easy way to publish content in different formats (spreadsheets, HTML, PDFs, etc). Orcus involved a very iterative process where I was changing the spreadsheets, building the Markdown files from the spreadsheets and then changing the PDFs to reflect the Markdown changes - and that was all easy via GitHub.
But that entirely depends on how you're planning to release content and what your workflow involves, of course!