Shea Megale, 12, has a new pet project. She has written a book about her best friend, a dog named Mercer. Shea has spinal muscular atrophy, an illness that confines her to a wheelchair. Mercer was trained to help Shea do things like open doors and turn on lights. In Shea's book, Marvelous Mercer, the dog does even more, including ice skating and swimming with friends. "I can't imagine my life without him," Shea told TFK.