In Floating City: A Rogue Sociologist Lost and Found in New York’s Underground Economy, Columbia University sociologist Sudhir Venkatesh studies New York City’s criminal underworld.

What surprised you most in your interviews with prostitutes and madams?

New York sex workers aren’t all drug addicts. They are likely to be white and middle class, and often considered [prostitution] a profession. Maybe that’s crazy, but in New York there aren’t many great options if you lack education or connections.

You also profile a drug dealer named Shine who was trying to acquire wealthier clients. What pitfalls did he face?

Shine tried to move from dealing crack to selling cocaine, to break out of the geographic and class boundaries of a Harlem drug dealer and into New York’s middle- and upper-class worlds. He was a businessman, but he had to learn to operate in a new culture. He couldn’t take the rules of the Harlem streets into Wall Street and Midtown bars. He had to dress and hold himself differently and talk to finance people and hipsters in art galleries. The book is about people trying to get out of the boxes that sociologists like me put them in.

In one boundary crossing, Shine meets Analiese, a white heiress. What did they have in common?

There is an aspirational quality to New York—wanting to make it on your own. Analiese didn’t want to be just the daughter of a wealthy family. The illicit economy let her reinvent herself—by becoming a madam and running an escort service. Analiese and Shine went into business together.

You write that many upper-class people have a sense of “serene entitlement.” Are the rich really different from you and me?

The sociologist in me believes in hierarchies: there are people on top and people at the bottom; people who get second chances and people who don’t. If you have resources in this city, you can get up again. Watching the underground taught me that without resources, that’s very difficult.

You almost break down when you witness a beating at a strip club. What got to you?

After studying the underworld for 15 years, I started questioning my motives. Was my writing helping anyone? My self-doubt reached a climax while I was going through difficulties in my personal life. Sociology has a certain hubris: you don’t share the problems of people you study. But as I gravitated to ne’er-do-wells, criminals, the folks nobody wanted, I started to see a part of myself in them, [a part] that also felt marginal and searching for a community. They understood me better than I understood myself.