PW: During the 1933—1934 war on crime detailed in your book Public Enemies, your grandfather was a deputy sheriff who helped man a roadblock trying to stop Bonnie and Clyde. What impression did his stories of that era have on you?

The stories my grandfather told always seemed so otherworldly to me; I was hearing them in the 1960s, but even then, 35 years after the fact, you couldn't believe it—it sounded like the wild wild west, something made up, and it's only by doing some reading that I found out how profoundly the country had changed as a result.

How much did you rely on recently disclosed FBI records?

About 50% to 70% of the book is pulled directly from these records, which are the primary new resource available to writers. I went into this thinking I was going to write mostly about the bad guys, and what startled me is the story that comes from the records about the FBI itself. I hadn't understood from everything else I'd read how transformative this was for the FBI. The FBI entered this period with no arrest powers, the guys didn't even carry guns (at least they weren't supposed to) and they come out of it the G-men of lore.

Were the records reliable?

You have to have concerns about reliability because in later years, especially, J. Edgar Hoover was notorious for inserting self-serving memos into files to cover his own ass. I found a few early versions of that. But in the end, the FBI files themselves, the sheer repetition and numbing detail that was in there, spoke to their veracity to me, and there were too many things that were openly critical or implicitly critical in the files.

Given the popular image of Hoover as a sinister control freak, were you surprised that there was material unflattering to the bureau still in the files?

I have no idea why they weren't cleaned up further. I was aware as I was writing the book that the portrait I would be writing of Hoover is far more positive than is normally the case. I worried a little bit that I might take some hits for presenting a portrait of Hoover that was somewhat positive. This 20-month period constitutes a portrait of Hoover before he was corrupted. I'm as cynical as the next working journalist, but he really was a good guy here. He was fighting the good fight, by and large. While the FBI did some bad things, and sometimes killed the wrong people, I think in almost every case it was done as a screwup rather than out of malice or some evil intent. What you do find is the genesis of the type of coverup it became popular to talk about later—their attempts to cover up their screwups.

Would the FBI have been transformed if someone other than Hoover had been in charge?

Yes. It did not take someone of Hoover's obvious talents to win the war on crime, as ugly as it was. Let's face it—they were chasing a bunch of bank robbers, and at some point you're going to get them. If you had a corrupt or amateurish chief where Hoover was, maybe the war on crime would have lasted five or seven years longer than it did. Give the man credit for introducing an incredible level of professionalism and, really, don't laugh, moral leadership.