In MBA school we are taught to negeotiate with a lot of figures, charts, graphs, etc. Once all the facts are known, the decision is simple. The problem with that is two fold: 1. They are typically based on projections that may well not be true (remember the Edsel and the Convair 880). 2. They ignore the feelings of the other person involved, and feelings are very important. Sometimes (often) a decision is made that is not to the person's best interest simply because of feelings.
This book breaks down the five core emothions of feeling appreciated, alone, imposition, put down, trivialized. It covers business negeotion, but perhaps even more important is negeotiating with teens (but not two year olds), the mentally ill (ex-wives included), the drunk in a bar.
The techniques described here are given examples in buying a small item, presenting a case to the Supreme Court, to discussing border disagreements between a couple of nations. In short, we all negeotiate all the time, it works best when both parties feel that they got the best of the deal.