The Inner Level: How More Equal Societies Reduce Stress, Restore Sanity and Improve Everyone’s Well-being. By Richard Wilkinson and Kate Pickett. Allen Lane; 352 pages; £20. To be published in America by Penguin Press in January 2019; $28. THERE is something peculiarly haunting about the recent suicides of Kate Spade, a well-known designer, and Anthony Bourdain, a chef and author (see Obituary). E