How do I rearrange photos?
If you would like to rearrange interior pages that are already in your book one-by-one, you may do so from the Book View by holding your finger down on the page you want to move, then dragging the page from one position in the app to another. The other pages will all move either forward or backward in your book to make room for the repositioned page.
Unfortunately, there is no way to automatically rearrange photos once they've been added to your book. If there are a lot of photos, you may want to delete them and then re-add them in the correct order. You can add photos to your book chronologically by tapping Add Photo, selecting the photos you would like to add, and then tapping 'By Date Taken'.