I have a lot of book typesetting and test Affinity Publisher from time to time. I have always tried to publish a project. I have not yet been able to set a single book with Publisher.
It is simply impossible to work professionally with Affinity Publisher (neither v1. 7. 3 nor Beta v1. 8. 0. 523).
The orphan and widow settings are a joke and so not usable. Footnotes are completely missing. Book function not available. The speed is so slow that it is unacceptable for a modern program. All in all, in my opinion the software has no sense in this way.
For a few flyers or business cards there are enough alternatives. But for book typesetting?
Serif I think this will take few years befor Publisher can be named so.