"Otherland" is a private virtual reality network in which rich people make their own virtual immensely realistic worlds. The plot focuses on a number of characters from across the world who end up entering Otherland with the usual quests against the bad guy and all. Great series, and Williams clearly has loads of fun writing new virtual worlds all the time - there's gotta be well over a dozen of them, probably more actually. Which means that while the premise is obviously sci-fi, some parts read more like fantasy.