By Ron Charles, The Washington Post Margaret Drabble has written a novel about aging and death, which for American readers should make it as popular as a colostomy bag. That’s a pity because Drabble, 77, is as clear-eyed and witty a guide to the undiscovered country as you’ll find. The ominous title of her new book, “The Dark Flood Rises,” comes from a poem by D.H.