You can copy photos from one Chatbook to another, so you don't need to upload them twice. This is also the way to merge or combine photos from two books into one.
How to copy photos to another book in the app:
Tap the book you'd like to copy photos from.
Tap and hold a photo.
Tap any other photos you want to copy.
Tap the copy button (two squares) at the bottom of the screen.
Select the book you'd like to add the photos to.
Want to move photos within the same book instead? See How do I Rearrange Pages in a Monthbook or Monthly Mini?
To learn how to share photos from one Chatbook to another from Chatbooks.com, see How do I share photos from one Chatbook to another on the web?
Looking to merge two Chatbooks accounts? See the merge section in How do I log in or fix login problems?