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.
Pareto optimal is definitely a core concept in game theory. It says that no other vector beats it in every dimension (or at least as good in all but one, and better in at least one).
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.
https://en.wikipedia.org/wiki/Tragedy_of_the_commons