A tetralogy of books by TadWilliams about a secretive order of superrich, superpowerful folk who have created this online construct in VirtualReality called "otherland." Something sinister about it (naturally).

1. OtherlandCityOfGoldenShadow (1996)
2. OtherlandRiverOfBlueFire (1998)
3. OtherlandMountainOfBlackGlass (1999)
4. OtherlandSeaOfSilverLight (not yet published)