I loved
Medea. Especially the worldbuilding; have only dim memories of the stories themselves.
There's a more recent shared-world science fiction book, called
Murasaki, edited by Silverberg, with stories by Poul Anderson, Greg Bear, Gregory Benford, David Brin, Nancy Kress and Frederick Pohl. Everyone involved was a Nebula winner.
The worldbuilding was placed at the end, and was more interesting to me than the actual stories, although those were also good.