[lynal]

There are many sources to develop an understanding of game theory. To build mastery in game theory, check out Osborne and Rubinstein's text. The authors offer it as a free download (http://arielrubinstein.tau.ac.il/books.html).

This is the text used by advanced graduate students, the material is explained precisely.

[TheGorramBatman]

It's a pretty intro level book, but a great one.

I'd say its suitable for maybe junior level undergraduates.