Apple is discontinuing its Photo Print Products service, which has been integrated into iPhoto since its launch in 2002. The service expanded from simple prints, to albums, photo books, and calendars. It stayed around on the Mac when iPhoto was replaced with the Photos app a couple of years ago, but the service never made the leap to iOS.
Later this year, Apple will stop offering the service altogether. A new message in macOS 10.13.6 Photos app says that final orders for Apple’s built-in service must be placed by September 30, 2018.
I haven’t used any of the new services Photos works with, but we have several Apple-printed books around the house, and we really enjoy them. I guess it will be time to branch out to a third-party service next time we want to create one.