Template for Ebook-Reader
This template makes easy to generate PDF file to read it on Ebook-Reader. In fact I'd trained it on Kindle, so perhaps it would be reasonable to correct the margins if needed.
The main problem with PDF's on 6-inches screens is lack of PDF-reflow function, or this function working badly. Why not just generate the PDF file well-fitted to the screen?
LaTeX ePub / eBook Template
This document shows how you can get ePub/eBook-like formatting in LaTeX with the memoir document class. You can't yet export directly to ePub from writeLaTeX, but you can export to PDF. To get ePub, you can download the LaTeX source from writeLaTeX and run it through a format conversion tool, such as htlatex to get HTML, and then go from HTML to ePub with a tool like Sigil or Calibre. See this thread on Stack Overflow for more advice.
Book Template for Amazon KDP and Google Play (e-book and PDF)
This template allows you a quick start creating books with LaTeX that you can directly publish on Amazon, Google, and Leanpub as e-book or printed edition. Check out the accompanying book "Better Books with LaTeX the Agile Way" for step-by-step instructions for this template: https://amzn.to/2Jiwpzh
(02/08/2020: fixed issues relating to TeXLive2019 upgrade. pdfLaTeX PDF output is no longer working properly but the HTML output is fine, so is the XeLaTeX PDF output).
Testing tex4ebook to generate basic ePubs
A very experimental hackety hack to export ePubs from LaTeX on Overleaf, using tex4ebook. After creating a new project from this template and when compilaton has completed, download the generated .epub file using the steps described here.
In this sample set-up, the .epub export will only be triggered if the project is set to compile with pdfLaTeX and will likely fail with many packages; this is a very basic example and this is a hackety-hack.
See the tex4ebook Github repository for documentation and discussion; though bear in mind that . Overleaf does not necessary have the most up-to-date tex4ebook release.