You can, of course, increase or decrease the number of pages. Please note that a different minimum number of pages applies for each photo book type (photo booklet: 16 pages, digital photo book: 24 pages, real photo book: 26 pages).
(1) Example: Delete page view in the photo book configurator:
(2) Example of delete page view in the preview view:
(3) Example of the Add pages view in the photo book configurator (either via the “+2” button OR directly specify the ultimate number of pages via the dropdown):