I have a rationalist/rationalist-adjacent friend who would love a book recommendation on how to be good at dating and relationships. Their specific scenario is that they already have a stable relationship, but they're relatively new to having relationships in general, and are looking for lots of general advice.

Since the sanity waterline here is pretty high, I though I'd ask if anyone had any recommendations or not. If not, I'll just point them to this LW post, though having a bit more material to read through might suit them well.

Thanks!