Sadako and the Thousand Paper Cranes by Eleanor Coerr, 1977

Based on the true-life story of Sadako, a Japanese girl who develops leukemia at age eleven. While Sadako is in the hospital undergoing diagnostic tests, her best friend brings her a piece of gold paper, which she folds into an origami crane. She then reminds her of the story of the crane that lives for a thousand years. If a sick person folds one thousand paper cranes, she will become healthy again. Sadako began folding cranes, hoping to reach one thousand cranes so she could live, but she died before the cranes were all folded. Recommended.