Stay away from Sphinx. It's terrible.

It has
* extremely limited markup (no bold and at the same time italic text, no text-colour, no fine control over tables)
* Bad pdf output (tables with column / row spanning is broken; image placement is restricted)

If you want to do good writing, use LaTex or Asciidoc (via asciidoctor)!
Asciidoc is really great, if you want a easily human-readable source. (It has none of the problems mentioned above).