Story: Substance, Structure, Style and the Principles of Screenwriting by Robert McKee - 477 pages.
A comprehensive guide to the essentials of screenwriting and storytelling, using hundreds of films as examples, and taking the writer through all the critical points which allow him or her to create a screenplay which both works and sells. 
"Story" deciphers the guiding structural principles that animate every classical and award-winning film, ranging from "Citizen Kane" through to modern acclaimed works like "The English Patient".