“When people think of the crack epidemic, they think of crime,” the journalist Donovan X. Ramsey tells David Remnick. “But they don’t necessarily know the ways that it impacted the most vulnerable—the ways that it changed the lives of people who sold it, who were addicted to it, who loved people who sold it or were addicted to it.” Ramsey’s new book, “When Crack Was King: A People’s History of a Misunderstood Era,” weaves the stories of four people who survived the epidemic into a historical analysis of how crack led to the erosion of dozens of American cities—but also of how the crack epidemic eventually ended. “I didn't know what life was like before crack,” Ramsey, who was born in Columbus, Ohio, in 1987, says. “I wanted to understand the ways that it shaped our society.”