LOS ANGELES (Reuters) – Judy Blume, the author of young adult books “Are You There God? It’s Me, Margaret” and “Tiger Eyes,” was diagnosed with breast cancer this summer and underwent a mastectomy, she said on her blog on Wednesday. Blume, 74, one of America’s most famous authors of young adult fiction, said that a month after her surgery she is recovering in New York. She also described the shock of learning from her doctor in June that she had breast cancer, given that she had no family history of the disease. …