Once it was The Shadow radio show; now it's the podcast Serial. Is every old storytelling medium new again? Frank Rose, author of The Sea We Swim In, concedes that some things remain sacred--from the power of a great hook to the hope that great stories never end. But he also thinks the Internet has led to new kinds of stories, ones that are not just entertaining, but immersive, and whose worlds are more richly imaginative than ever--even as they leave increasingly little to our imagination.