This user tip has the links to some discussions on printing books, now that Apple stopped the service:
https://discussions.apple.com/docs/DOC-9861/edit?ID=9861&draftID=12256743
Just in case the links still do not work, I have pasted it below:
Apple stopped the Print Services for Aperture print products and iPhoto projects on march 21, 2016.
When we try to order a book, we will see this message.
And the menu entry "Aperture > Aperture Plug-ins" to download the book plug-ins for third party photo books, but this menu entry now opens a completely different page: http://www.apple.com/osx/photos/
The problem is, that the Photos for Mac application does not support Aperture books well. Photos uses different Themes and cannot recreate Aperture's custom layouts. Book projects will usually migrate as albums to Photos, if Photos cannot recreate the book. So we will have to cretae a new book in Photos from the album. How Photos handles content and metadata from iPhoto and Aperture - Apple Support
One way to get Aperture books printed is to print the book to PDF and send this PDF file to a different service.
See the link below on how to save the PDF file for printing with PrestoPhoto posted by PrestoMeghan:
Re: Re: how to export a book made in Aperture to make a similar book in Photos?
In this discussion are also reports by kgem and Astro7x about the first experiences with this service.