Deleting unused paragraph styles in one fell swoop
I highly recommend that Adobe updates a feature to delete all unused paragraph styles in one fell swoop instead of a file by file case.
Additionally, have this option available at the book level. If a style is used /anywhere/ in my book, I want to keep it, but if a style isn't in use in any of my book documents, then I'd like to delete it.
Nick Cuccia commented
You should be able to choose "Select All Unused" in the Paragraph Styles panel's options menu and click the trash can to delete.