So you want to author your own open textbook...Here are the steps you need to take!
Creating the content - Consider what the scope and purpose of authoring your own book before starting. Make sure to give proper attribution to others' work and if you use other OER as your basis, make sure that you are following Creative Commons licensing rules.
Put your content in a professional format - There are many tools for creating professional looking ebooks. Some of the most popular are Open Author, and Press Books.
Make it accessible - Accessibility is more important than ever. Ensure that your content can be read by all by following accessibility standards when you create it.
Decide your license - You'll need to assign a Creative Commons license to your work in order to make it usable and shareable by others. You can read more about the licenses and how to assign them at Creative Commons.
Make it editable - Another consideration is whether you want to allows others to edit and add to your work. If you do, make sure that you make editable versions of the book available.
Give it a home - Your new book needs a permanent place to call home! Consider your institution's repository or website.
Spread the word - Tell people about your new book by submitting it to popular OER repositories such as Merlot or OER Commons.