The world of fanfiction climbed to new heights this year with the film release of Fifty Shades of Grey, which has pulled nearly $162 million at the domestic box office. The book started as Twilight fanfiction: Edward the vampire became Christian Grey the human sadist. Fanfiction -- all one word -- is just what is sounds like, fiction written by fans of existing work using the same characters or other elements of the original. And, despite its reputation, it’s huge. We get an overview of the field.