The Mushroom Man has arrived at its thirtieth anniversary despite breaking every rule of picture-book storytelling. It is not a story about children: The only kids make a cameo appearance to taunt the mushroom man in the street. It is not a heroic story: The mushroom man toils away in a mushroom farm, coming to resemble a mushroom himself.The story doesn't teem with personalities: The mushroom man's existence is solitary. So why does it endure?...