GitHub Issues
All content related to this book is hosted at the GitHub DinisCruz/Book_Generation_Z_Developer repo.
This repo not only contains all text (in Markdown), but also all pending issues and ideas. I'm using the exact workflow and ideas presented in this book in the development of this book :)
You can read more about GitHub and Git in the respective chapters, but if you want to be involved in an open source and Creative Commons project, this would be a good place to start.
Here are the current list of issues (as of the last time this book was generated) that you can help out
Issues list
Using GitHub api on 08 Oct 2018 the following 5 issues had the show-in-book label: