The Writer's Journey Mythic Structure for Writers
by Christopher Vogler
Chris Vogler has taken Joseph Campbell's work (books
, influences) and simplified it for popular fiction and movies. (Okay, he's a studio executive so his experience is film, but this book is still helpful to novelists.) 
The Key: How to Write Damn Good Fiction Using the Power of Myth by James N. Frey is another approach to Joseph Campbell's work. If you read the comments/reviews on Amazon, you'll find those who prefer Frey, those who prefer Vogler, and those who prefer Campbell -- yet more proof that we all respond to different presentations of information. This one is more geared to novelists, if that makes a difference.
Save The Cat! The Last Book on Screenwriting You'll Ever Need by Blake Snyder. There are many different processes for outlining and developing a story, whether it's a novel or screenplay. I have been using this one on my most recent project and have discussed it in my blog at length. So far, so good. If you want an easily understood and logical process, you might want to give this one a try, too.
Making a Good Script Great
by Linda Seger
A book on rewriting, this has some clear and solid info and examples of story structure using some fun 80s movies (Back to the Future, Romancing the Stone, for example) to illustrate.
Screenplay
by Syd Field
The Grandaddy of them all, the book that first broke contemporary story/film structure into three acts.
