The best book on negotiation is Bargaining for Advantage by G. Richard Shell from Wharton. I would reading Getting to Yes first to get the basics though.

http://www.amazon.com/Bargaining-Advantage-Negotiation-Strat...

http://www.amazon.com/Getting-Yes-Negotiating-Agreement-With...

Think these books are of much help to someone who isn't already good at bargaining? They look ripe for the 'squeezed books' treatment:

> Focusing on six key psychological leverage points...

Should be easy to summarize.