If New York City had its own currency, Ed Koch would surely be on one of the bills. He left office in 1989 but still stays in the public eye any way he can, from being a pundit and author to a TV judge and movie columnist. But Koch was more than a folksy catchphrase (“How’m I doin’?”) or a brash personality. He came into office as the city faced bankruptcy and put in policies that reinvented New York physically and financially.

Historian Jonathan Soffer’s biography, Ed Koch and the Rebuilding of New York City, is a richly sourced and detailed assessment of the mayor, a city in the financial trenches and urban politics. We spoke with Soffer, a professor of history at NYU-Poly, about working with Koch, his enduring public persona and the real cause of New York City’s money problems.

New York Press: What was your relationship with Koch during your research and writing?

Jonathan Soffer: Cordial but independent. He did read the draft and did comment on them. The agreement was that he would tell me when he thought I had gotten my facts wrong but the interpretations were entirely mine and he pretty much stuck to that. He was really a gentleman about that. I actually wonder if I myself would be so calm if somebody were writing a biography about me.

You write about his most heated battles as mayor. What do you think of his personality and style?

There were beneficial aspects to it. As I quote Sen. Daniel Moynihan in the book, he gave New York back its morale. But his bluntness raised suspicions among many members of minorities that he was not protecting or promoting their interests.