When I think about the tags I might use to describe a book, the first that comes to mind is author. There are plenty of books, such as anthologies, that feature many writers and prominently mention the editor. Even with books by a single author there are plenty of other creative people associated with the publication. Here are a few that come immediately to mind.
- agent
- editor
- cover artist
All of these provide meaningful groupings that are not necessarily just groupings of authors.