A Brief Introduction to the Basics of Game Theory

I think a basic overview of game theory should also discuss Pareto optimality to some extent. You can have 100% of participants operating in a locally-ideal way while still creating problems in aggregate.

Why Flip a Coin is a really great book about game theory. Easy to read, very little assumed knowledge, and lots of very interesting and counterintuitive examples and situations. Also, despite the introductory nature - still gets into the math in a rigorous way.