Maybe you read about Amazon's Worlds, which aims to monetize fanfic by selling it ?to the devoted. And reworked fanfic regularly pops up on the best-seller list, with several writers scoring six- and seven-figure advances.

Despite that success, few know much about fan fiction, in which amateurs write and share unauthorized adventures featuring established characters. Anne Jamison, a professor at the University of Utah, guides the curious down the rabbit hole in Fic: Why Fanfiction Is Taking Over the World, a lively collection that pulls together contributions from fic writers, novelists, academics, attorneys and even a couple of Hollywood actors -- like Buffy the Vampire Slayer's Amber Benson -- to educate the neophyte.

The essays are full of wonderful nuggets. Fanfic more or less began at the turn of the century with Sherlock Holmes, but it took a leap forward during the late '60s with the near-simultaneous appearance of Star Trek and cheap mimeograph machines. Holmes and Trek fic share a fascination with turning the central characters' friendship romantic. Kirk/Spock stories gave birth to slash fic -- an erotic subgenre, often gay, pairing major characters (and usually written by women).

Indeed, no less than Star Trek creator Gene Roddenberry himself winked at the Kirk/Spock stories in the novelization of 1979's Star Trek: The Motion Picture by having Kirk dismiss the rumors, saying it wasn't the homosexuality that bothered him, but the idea he'd pick a lover who mated once every seven years like a Vulcan does. (And it was in a footnote! Extra points for geekiness there.)

Hollywood hasn't always had such a relaxed attitude toward fanfic, as Heidi Tandy, a copyright lawyer and fanfic writer, recalls in an essay about the parade of cease and desist orders that came from Warner Bros. to shut down a Harry Potter gay fanfic website because the studio was concerned younger readers would stumble upon it. But after J.K. Rowling revealed Dumbledore was gay and Daniel Radcliffe appeared nude in the play Equus, the requests ceased.

And not all fanfic is necessarily supportive of the author. Twilight fanfic exploded after readers hated what Meyer ?did with Bella and Edward in 2008's Breaking Dawn and wanted to create an ending they liked -- and the book reprints a fascinating lost interview with James (under her fanfic pen name "Snowqueens Icedragon") that reveals that's what motivated her to start writing.