I´m working with a plugin for pressbooks. We had something in the past, but is not working as it should be, that´s why we decided to start and make it much simple before to start to upgrade with features.
We did finish the alpha (to make it works).
Now betha (to make it for the pressbooks comunity, not just specific for my site)
Now, PB use several schema classes
For books: books
(as you can see, some fields are empty, we will create for pressbooks inside of pressbooks core if @ned you are agree. We believe the edition of the book is very important, book format… can be good if we allow to download the book, illustrator is missing too, and i don´t know about number of pages)
For chapters: webpage
(we need to think about that types because some are missing but we need a better research)
In order to make the metadata more flexible and because we are creating educational metadata (by default), we are creating other schema classes
and in the future, we will use website classes from schema for the root theme http://schema.org/WebSite