It appears that none of the Solidworks Electrical BOM reports are affected by the "One Report By Book" checkbox option found under the Layout Tab in Report Properties. I've been trying to generate book-specific BOMs but it never works. All I can ever get is a single BOM in the first document book, but never any BOMs in any of the other books.
According to this link, the feature is supposed to work:
My VAR says that Solidworks Development has a ticket open for this issue and that it will be addressed in future Service Packs.
Are there any work arounds that I can use in the meantime?