When we go to Google Colab there are some options, and we are going to focus in the option GitHub. You have to enter a GitHub URL or search by organization or user. I searched, for example, my repository: BARCELONABIM.
You can click on the link of your repository. The best way to work is to make a copy of the book in Google Drive. You have to go to File-save a copy in Drive. It works in the server of Google.
You can also to save the book in GitHub or to download.