I found the book made me uncomfortable, in sort of the same way I feel when I'm watching a masterfully-made infomercial. This, to me, is a sign that it was working. ;) If the sport of negotiating was as natural as breathing for me I wouldn't be reading a book about it!

Negotiation Genius is probably the most accessible one:

http://www.amazon.com/Negotiation-Genius-Obstacles-Brilliant...

Winning Through Intimidation was a fun read, especially if you're into real estate. Apparently the book is worth a lot now (I had no idea, I have an old hardcover version that I don't even see here)

http://www.amazon.com/Winning-Through-Intimidation-Robert-Ri...

http://www.amazon.com/Game-Set-Match-Winning-Negotiations/dp...