Aristotle's Poetics (Dramabook,)
The original, Aristotle's short study of storytelling, written in the fourth century B.C., is the world's first critical book about the laws of literature.  Sure, it's 2400 years old, but Aristotle's discussions--Unity of Plot, Reversal of the Situation, Character--though written in the context of ancient Greek Tragedy, Comedy and Epic Poetry, still apply to our modern literary forms. The book is quite short, and Aristotle illuminates his points with clear examples, making thePoeticsperfectly readable, the better to impress people at parties when you say, "Of course, as Aristotle says..."