Sorry I can't help. I have the same question. I loaded Mimeo and Motif into Photos (Mojave) and they seemed to work OK, but I haven't made a book yet. What I find really bad is there is no longer option to print the book to a local PDF file. In the new set-up, when you print and then make a pdf, it only makes a contact sheet with the photos you have chosen to be in the book. Also, the online services (shutterfly, mixbook etc.) do not offer to save the book as a pdf (even after you have paid to have the book printed).
That being said, mixbook works pretty well and the book quality was OK. But, the lack of a pdf option makes it the last time I'll use it.
I also read about blurb.com, which allows to save as a pdf but the software is not so great (but it allows a lot of tweaking, just not a lot of good template options based on the review I read).
Hope this helps.