Apple is now promoting their word processing app with the pitch that you can use it to publish a book to Apple Books:
Publish your book directly to Apple Books from Pages on your iPad, iPhone, Mac, or online at iCloud.com. With Pages, you can create a book, then publish it directly to the store in Apple Books. You can customize your book during the publishing process: add a cover, set your price or offer it for free, add tags to specify age groups or subjects, set up a pre-order, customize availability by date and country, and more. You can also update an already submitted book.
This is going to be a great option for those whose books don't need a lot of professional editing and/or formatting. (That isn't snark; my workbooks need a lot of formatting, so this option is no good for me.)
This update doesn't bode well for the long-neglected iBooks Author. That app has only bee updated an average of once a year since 2014, and Apple cares so little about it that Apple hasn't even changed the app's name yet.