@cornychat is super useful you can easily make private or public rooms, zap, sign in with Nostr, or stay anonymous. Would be a great resource addition to the list

https://nostr.org/

And I'm sure you can find some other gems on my own curated list here https://ccns.nostrver.se/

That relay wizard guy seems like it might be a helpful tool. I haven't looked into it, but maybe you can for your book.