Thinking Strategically: The Competitive Edge in Business, Politics, and Everyday Life (Paperback)
by Avinash K. Dixit and Barry J. Nalebuff

An excellent reference on Game Theory and competitive strategies with many case studies but little math.

Co-Opetition : A Revolution Mindset That Combines Competition and Cooperation : The Game Theory Strategy That's Changing the Game of Business (Paperback)
by Adam M. Brandenburger, Barry J. Nalebuff

A great companion to Thinking Strategically : The Competitive Edge in Business, Politics, and Everyday Life by Nalebuff, this great book that shows how to get paid to play the game by using game theory.