ox-epub VS olivetti

To export an org file to epub use ox-epub, and you'll get an option for epub in the normal org-mode export with C-c C-e.

I've recently been using org-mode (well, org markup) to mark up a few existing public domain books, and then using ox-epub to generate EPUB ebooks. It's been working well for me for the prose that I've been working with, and I've also tested HTML export to make sure it looks how I'd expect. It's a super simple workflow that generates results I'm very happy with.

I also use writeroom because I prefer its simplicity, but worth mentioning that olivetti is the more popular writing mode.

There are nice looking distraction-free setups with https://github.com/joostkremers/writeroom-mode or https://github.com/rnkn/olivetti or https://github.com/joaotavora/darkroom or https://github.com/rougier/nano-emacs

For batteries-included packages that give you dedicated prose-writing modes, see also olivetti and writeroom-mode.

You could use olivetti-mode or Writeroom mode.

Another option is the Olivetti package. https://github.com/rnkn/olivetti

Don't have a specific tutorial except to suggest setting org-mode to use olivetti and a nice variable pitch font for writing prose. You might also like the poet theme.

If you want to try out some third-party packages in the beginning, I think the most "bang-for-your-buck" you'll get is with Avy. Also, expand-region. And specifically for writing: olivetti-mode, flyspell, dictionary, and Nicolas Rougier's Nano and Elegant Emacs setups.