The unreal and the real by Ursula K. LeGuin

The Unreal and the Real: selected stories of Ursula K. Le Guin. This is a book of short stories by a grand mistress of Science Fiction & Fantasy. The second volume includes the story The ones who walk away from Omelas.
You don't have to read both books. Just read the stories that interest you.

My apologies for originally posting just the first volume, which did not contain the short story that was suggested at the last meeting.