There they lay, outside time and space, each hanging in its separate limbo, each a planet called Earth. Fifteen globes, fifteen lumps of matter sharing a name. Once they might have looked the same, too, but now they were very different. One was comprised almost solely of desert and ocean with a few forests of gigantic distorted trees growing in the northern hemisphere; another seemed to be in perpetual twilight, a planet of dark obsidian; yet another was a honeycomb of multicolored crystals; and another had a single continent that was a ring of land around a vast lagoon.
The wricks of time, abandoned and dying, each with a decreasing number of human inhabitants for the most part unaware of the doom overhanging their worlds--these worlds existed in a kind of subspacial well created in furtherance of a series of drastic experiments. Thought provoking . . .
By the author of the classic Elric of Nelnibone sword and sorcery series