If you’re partway through editing your book and realize that a different theme may have been a better choice, you can change this by clicking on the change theme icon in the lower-right corner of your screen (See Below).
This will open the theme selection panel, allowing you to choose a different theme if you wish.
If you've made changes to your theme before changing to a new one, those changes will be lost.
If you had already added photos to your book, the editor will try to transfer the same photos to the new theme. Because the new theme may not have the same number of photo placeholders on each spread, some changes may occur.