Getting to Yes by Roger Fisher and William Ury (and Bruce Patton)

A book about "negotiating agreement without giving in."  This is one of those books everyone should probably read as it provides good advice on a) not bargaining over positions; b) separating people from the problem; c) focus on interests, not positions; d) invent options for mutual gain; e) insist on using objective criteria, and then trying address various concerns and questions.
Short, straightforward, and sensible.