Can I change (the order of) photos in the Travel Book?

Sure you can! You can do this manually in the Edit Travel Book modus by dragging and dropping them into your preferred position. 

How to drag and drop a photo? 

Simply tap or click a bit longer on the photo. That will enable you to move it to the preferred position or page. 

I want to add photos to my Travel Book. How can I do that? 

The information in your Travel Book is the same information that you've saved in your trip. So if you want other photos in your Travel Book you'll have to add those to existing or new steps in your trip.