So I quit my job to focus on my startup...
Mz: I had a class called "Negotiation and Conflict Management".  The two required texts for it were "Getting to Yes" and "The Mind and Heart of the Negotiator".  My recollection is that these are the only two books on the topic (or were at the time) that are based on research.  "Getting to Yes" is short and an easy read.  "The Mind and Heart of the Negotiator" is a much meatier book.  I recommend it often.