Rapp, the author of "Poster Girl," has already written her own story as a young woman growing up with an amputated leg. In her new memoir, however, Rapp tells the story of her son, a child diagnosed from birth with a degenerative illness that she was told would end his life by the time he was three. Rapp is "a beautiful writer," says Nelson. "It's hard to believe but in this book there are also lighter moments." In the end, says Nelson, this searing memoir is "a beautiful rumination on parenthood and identity."