In her wonderful cross-genre book The Creative Habit , choreographer Twyla Tharp calls a work’s organizing principal its “spine.” She writes: The spine is the statement you make to yourself outlining your intentions for the work. You intend to tell this story. You intend to explore this theme. You intend to use this structure. The audience may infer it or not. But if you stick to your spine, the piece will work. I am such a student of the way structure can support meaning in literature that I had Tharp's notion tucked away in my consciousness while reading my book club’s recent pick, Colum McCann ’s 2009 National Book Award winner, Let the Great World Spin . The book begins with the description of a disparate crowd of onlookers brought together by a 1974 public spectacle—specifically, Philippe Petit’s infamous 110-story walk between the World Trade Center’s twin towers. Because the thread connecting the interrelated stories comprising McCann's novel is as tenuous as Petit...