I added that library card for the book I just read, added it to my bookshelf (a Nostr directory for publications that can contain subdirectories/sub-bookshelves), and then published a rating for it. You can also publish highlights, labels (we call them "booklists"), or comments. Prototype of the nested directory structure here: https://jumble.imwald.eu/directories Here is the spec for it: https://jumble.imwald.eu/notes/naddr1qvzqqqrcvypzplfq3m5v3u5r0q9f255fdeyz8nyac6lagssx8zy4wugxjs8ajf7pqqyxu6mzd9cz6vp5e0vxdq