Never Split The Difference by Chris Voss
8.5 out of 10

Having been both a hostage negotiator for the FBI and a Harvard Business School instructor, Voss has an abundance of intense and enlightening anecdotes.  Gathering information and understanding the emotions of your negotiating counterpart requires finesse.  And ultimately, there is a rich psychological toolkit for getting everything you want (unharmed hostages and captured criminals, for example).  In a single battle, no tactic has a 100% success rate, but experienced negotiators continuously improve their odds.