In this thoughtful treatise spurred by the 2015 death of African-American academic Sandra Bland in jail after a traffic stop, New Yorker writer Gladwell (The Tipping Point) aims to figure out the strategies people use to assess strangers-to "analyze, critique them, figure out where they came from, figure out how to fix them," in other words: to understand how to balance trust and safety. He uses a variety of examples from history and recent headlines...