[jaysonelliot]

That's a great point. For example, my wife probably knows me better than anyone in the world. She's very good at seeing a book and knowing I'm probably going to like it. That includes your example of "this is a good book for a trip" vs "this is a good book to read at home, at night." But even she gets it wrong about 20% of the time.

In order to be able to really recommend something as multi-faceted as a book, movie, or song, you have to know a person on pretty much every level. I suppose seeing a person's entire social graph, search history, LLM history, media consumption history, and browser history might get you close, but it's still a Hard Problem™.