So, many people use outline notes for book notes, and they have many links that go straight to it; and also many headlines. There should be a feature to “show headlines as notes” in local graph view - it can be messy if it happens in the global graph view -. This will help finding what someone needs from the book fast.
This can help re-imagine the graph view in book outline notes like this one (this is a small 90 pages book; imagine if it’s an outline for a thesis or 800-pages book!):