Running header variability for different types of books

[Omikhleia]

in a technical book, the odd header is the section title (but could also user lower levels), and the even header is the chapter title.
In a novel, the odd header is the chapter title, and the even header is the book title.

Our current sectioning hooks do not allow easily configuring this layout difference (other than overriding their implementation, but there are other places when we'd need to know the layout - e.g. in master documents to know what to do with the book title)