To share/copy photos from one Chatbook to another Chatbook:
Log in to Chatbooks.com
Click Home at the top of the page, or click Account and then My Books.
Click the book you'd like to copy photos from.
Click "Rearrange pages" at the top right
Select the photos you want to copy over by clicking on them individually.
Click the two-square (copy) button at the bottom of the page
Follow the on-screen instructions.
Your photos will now be in your Chatbook of choice.
If you would like to share photos from one Chatbook to another on the Chatbooks app, see How do I share photos from one Chatbook to another on the app?