This is the standard b-school textbook for negotiations class. Very good.

To be clear and in response to other comment, you can't expect everybody to be rational. In my first mock negotiation in that class I got completely hosed. Turns out I totally trusted the other party not to lie. Lesson learned from the b-school *holes.... Part of the class was you have to know your own biases and anticipate some of the other counterparty's.

Chris Voss says that the approach on this book used to work until they figured out that it is outdated.

The basic idea there, is to prevent confrontation and trying to be rational.

However, people are not rational and emotions play a huge part in our lives so it should not be ignored and should even be leveraged.

Never split the difference is the book that builds on it and add tons of stuff about negotiation. It isn’t easily one of the best books I read (actually heard) and I highly recommend it.

I've heard this is good too - though I haven't read it.

Up! Great one, thanks for reminding me of it.