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I'm going to stick my neck out and say that River, not World, is the real title of this story.
Elena is a young woman from Earth who goes to a distant planet to live with the natives, a simple, happy people. There she becomes the wife of their leader, the King of the Golden River. His people live on an island with two volcanic peaks, and when one of them starts erupting, Elena begins to learn just how alien these people are.
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