'Isaac's Universe' is a Universe invented by Isaac Asimov for other science fiction writers to write about. Isaac's Universe: Volume One: The Diplomacy Guild, the initial collection of original science fiction short stories, was edited by Martin H. Greenberg and published in 1990 by Avon Books. It introduces the collaborative universe created by Isaac Asimov which eventually resulted in five volumes: three short story collections and two novels.
Volume One: The Diplomacy Guild is 258 pages long, not counting an additional couple of pages in back on the authors contributing their works. There is also an introduction by Isaac Asimov that is seven pages long. This was followed by Volume Two: Phases in Chaos and Volume Three: Unnatural Diplomacy. The novels are: Fossil by Hal Clement and Murder at the Galactic Writers' Society by Janet Asimov.
The premise of Isaac's Universe is that the Milky Way Galaxy in the future is populated by six high-tech, space-faring species:
Robert Silverberg, who wrote the first Isaac's Universe story, added the idea that there is a seventh, mysterious race which has never been seen, but which has left behind artifacts spread throughout the galaxy.