Silberengel on Nostr: The spec doesn't assume that a 30040 is a book, that's why it's that way. It could ...

The spec doesn't assume that a 30040 is a book, that's why it's that way. It could also be an index of articles or wiki pages from different authors. Or pages from various books from various authors in various editions.

That's why only the title is required, as everything has some sort of title.