Add, remove, and reorder book pages
You can add, delete, or reorder book pages. You can insert new pages anywhere in a book, except between the outside cover page and the inside cover.
Note: A book must have an even number of pages. If changing the number of pages creates an odd number of pages, Photos automatically adds or deletes a blank page to keep the page count at an even number.
Click a book under Projects in the sidebar.
Do one of the following:
Add a page: Select the page you want the new page to follow, then click the Add Page button in the toolbar and choose Add Page.
Set the exact number of pages in a book: Click the Book Settings button in the toolbar and drag the Number of Pages slider.
Delete a page from a book: Click the page to select it and press Delete, or click the Add Page button in the toolbar, choose Remove Page, then click Continue. You can also Control-click the page, choose Remove Page, then click Continue.
Move a page in a book: Position the pointer over a page number until the page button appears, then drag the page button to move the page to a new location. You can also select a page and then drag the page button.