This is the Markdown syntax. It's designed to be much easier to use than HTML or other languages and it's less intrusive when proofreading.
https://daringfireball.net/projects/markdown/syntax
But not all markdown supported should go into an ebook, not all ereaders support all XHTML. Just stick with basic Markdown. There is 00readme.md file included in the zip file.
I'll look into supporting the required meta data. I already have the author, title and language supported. I just need the unique id.
Examples of Markdown:
# This is header level 1.
## This is header level 2.
### This is header level 3.
*This is italic* text.
**This is bold** text.
This is inline code: `12345`
> This is a block quote.
> If the next line is below it, this line will be included and rewrapped as part of the block quote.
Paragraphs are separated by blank lines.
Focus on writing, not formatting.