I recently finished Points of Departure: Liavek Stories by Patricia Wrede and Pamela Dean. Liavek, the world in which these stories are set , was created by a group of authors (I think seven; the group included Wrede and Dean, anyway) in the 1980s; this collaborative venture produced 5 collections (all currently out of print). I’d heard of the original anthologies, but I never managed to get a hold of any of them. So when I saw some of the original Liavek stories had been re-issued I was eager to read them.
I enjoyed the anthology as a whole (rare for me; I’m not much of a short-story reader), but I think its strength really is the complex, colorful world of Liavek. I’m still trying to wrap my mind around how a group of authors could create a world together, and write so consistently (at least in the Wrede and Dean stories I read) of it. For me, world-building is really an act of discovery. I know a couple of things about the world and I learn more as I write.
But to create a world as a group, one would have to know more about the world before writing, I would think. Or, if one had a writing group and were sharing stories with them regularly, could it be an organic process in the same way as discovering a world solo?