Final Draft and Movie Magic Screenwriter (formerly Script Thing) are the leading screenwriting programs; to survive as a screenwriter, you must have one or the other—and many writers have both. Each program has its fans (famous and otherwise), and each can create a file readable by the other (though some cleanup may be required after file conversion).       

Story: Substance, Structure, Style and The Principles of Screenwriting, by Robert McKee - The preeminent book on story mechanics by the living master of the subject: Robert McKee. As McKee himself tells those who attend his 3-day Story course, everything in the course is contained in this book. The course runs $575; the book less than $25.

The Hero with a Thousand Faces, by Joseph Campbell - The classic tome by the world’s greatest mythologist; explains the basic elements which lie at the heart of all great stories, from the dawn of civilization to the present day. Dense but required reading for anyone interested in mythic structure. Among the most devoted followers of Campbell’s teachings: filmmaker George Lucas.

The Writer's Journey: Mythic Structure for Writers, by Christopher Vogler - Applies the mythic structure uncovered by Joseph Campbell to the screenwriter’s craft. Recommended reading for those interested in mythic storytelling.

The Screenwriter’s Legal Guide, by Stephen Breimer - The Screenwriter’s Legal Guide is far and away the best book on the topic; nothing else comes close. Written by one of the top entertainment attorneys in the business, this volume tells it like it is: what should be in your contract, what shouldn’t be—and what might be, if you know enough to ask (which, after reading this book, you will). An absolute must-have for the serious screenwriter.

StoryView v2 - If you like to outline before you write, this is the tool for you; if you’re not an outliner, StoryView will make you a believer. This program gives you the ability to outline your story in as much (or as little) detail as you desire, and to view the entire (or partial) outline on your monitor. You start with three acts, then add as many sequences, scenes, and beats as you like. Elements can be added, moved, deleted, colored, expanded, collapsed, you-name-it. There’s an onscreen timeline, a multi-tracking feature, and the ability to import/export from/to other programs such as Movie  Magic Screenwriter, Microsoft Word, etc.

Fatal Subtraction: The Inside Story of Buchwald V, by Pierce O’Donnell and Dennis McDougal - An unprecedented lawsuit offers an inside look at studio accounting practices, a chronicle of the arrogance of power, and a testament to the bottom line—where the show must go on, despite the fact that everyone involved seems to hate everyone else. Recommended—and fascinating—reading.