Is it obvious? Perhaps, but there are a lot of obvious things in life that must be told to us many times before we understand. Positional negotiation ("$40", "$150!", "$60", "$130", ...) doesn't guarantee an agreement will be reached, let alone a mutually satisfying one. The authors offer principled negotiation as an alternative process: separate out people from their interests, deal to the human factors with preparation and attention, then negotiate on the interests (what both sides need in order to have succeeded) by finding third ways forward in which both sides win. The book offers sample dialogues to show how this works in practice, and talks about the preparation you have to do to make this work. I'd have liked to see more sample dialogue, so the techniques seemed less like magic and more like something I could do, but I think it's enough to go on. Now all I have to do is find something to negotiate about ...