nostr:npub1m3xdppkd0njmrqe2ma8a6ys39zvgp5k8u22mev8xsnqp4nh80srqhqa5sf my point was that the 30040's have two uses. On the top level they are used as a book. On the second and deeper levels they are used as sections. 

Imagine there are thousands of books and tens of thousands of sections (all 30040 events).  How do I query for the list of books? IMHO there is a tag needed to identify the top level books.