Aaron Ruby and Heather Chaplin, authors of Smartbomb: The Quest for Art, Entertainment, and Big Bucks in the Videogame Revolution spent a while NPR’s Saturday Weekend Edition discussing “Role-Playing Games, Offering a New Reality” (audio stream) — and despite the title, it’s not about Baldur’s Gate or Final Fantasy, but about MMORPGs.
I haven’t listened to the whole thing yet, but it seems both introductory and yet nicely thorough, covering the basics of how they evolved from MUDs, for example.