The Writer's Journey by Christopher Vogler, and then Joseph Campbell's Hero with a Thousand Faces (which Vogler's book is based on).
Fascinating themes based on the 'monomyth', the idea that all storytelling, throughout the ages and across the globe, has common character types and structural elements. George Lucas was a big fan of Joseph Campbell and the original Star Wars trilogy played out his ideas with great effect!
This then lead myself onto Carl Jung who believed that we inherit all story telling elements from our ancestors and that we all hold an unconsciousness collective of character 'types' and religious symbology in our minds.
Enough to get you going...