I hear they've got these things called 'books,' with story, plot, character development and descriptions so real you can imagine the scene in high def. Crazy, I know!
I fear that with the rise of the e-book we'll start seeing restrictive licences and DLC for books as well.
Though, come to think of it, Charles Dickens's stuff was originally serialised in magazines, was it not? Which I guess was kind of an early form of DLC.
The modern form I suppose would be to buy the main novel, then pay extra for bonus chapters.