Printers Row Journal caught up with O'Reilly, for a phone interview from New York focusing on the "Killing" series, whose first installment, "Killing Lincoln," is being published for the first time in paperback this month. Here's an edited transcript of our chat.

Q: What was the original impetus for the "Killing" series?

A: Well, I had signed a contract with HarperCollins to do a sequel to (his memoir) "A Bold Fresh Piece of Humanity" (2008), which was a big best-seller. I was writing it, but then I said, "You know what? I'm repeating myself." I'd had (several) No. 1 best-sellers writing about contemporary things. So I went to the publisher and said, "I'm not comfortable doing a sequel here because I don't have enough new stuff for the book. But I'd like to start a new thread." I wanted to write about history, but in a way that regular folks would read it — not, you know, these big 800-page, tough-to-slog-through tomes. I wanted to do it in a form that everybody would enjoy, but also learn a lot. HarperCollins didn't want to do it. They said, "There are too many books about Lincoln." And I said, "I'm going to do it a little bit differently." But they didn't want to do it, so I took it to another publisher, who I'd worked with earlier in my career, and they took it. They didn't want to pay me a lot of money up front, which I got for my other books, so I took it on what they call the back end. The best deal I ever made! (Laughs.) "Killing Lincoln" sold more than two million copies, and is just coming out in paperback. It's a big profit center. And once we got started, it took on momentum, and here we are.

Q: Why is it, do you think, that readers find the subject of assassinations so intriguing?

A: I don't think it's the assassinations per se that the readers are interested in; it's what we bring to the whole story. Jesus, for example, was executed, and a lot of people didn't know that. Patton, we believe, was murdered, and a lot of people had no idea about that. So I think it's what we bring to these stories that drives the books, not just the actual killings.

Q: In the case of Reagan, you were probably always going to get around to him — although of course, he wasn't actually killed.

A: The title is a feint. He was intended to be murdered, and he was so close to death. We used the title because Hinckley wanted to kill him. So I think the title is accurate. But it'll be interesting to see how folks process this book.

Q: What did you learn about the assassination attempt on Reagan that we didn't know before?

A: Well, we take you through Hinckley's life. It's similar to the Kennedy thing, where we showed you a lot about Oswald and dispelled a lot of myths. Hinckley is less well-known than Oswald, but we trace him and find out how he got to the point where he was willing to shoot the president of the United States. He wanted to kill Jimmy Carter — very few people know that. He was stalking Carter, but couldn't pull it off. But his madness then became so intense that when he got a chance to get Reagan, he took it. So that's No. 1. No. 2 is, people just don't know a lot about Ronald Reagan. There's the myth. But they don't know a lot about how he assembled his power, what his mindset was, what drove the man. We tell that whole story in the context of the attempted assassination, and then how it affected his presidency, how he changed after he was shot. So there's a lot of new stuff in the book, a lot of stuff that will make people go, "Whoa! I didn't know that." That's what drives these books. They're entertaining to read, but you learn a lot.

Q: How did Reagan change after the attempt on his life?

A: Well, when you get shot at that age, your whole body and mind, your whole physiology, changes. And it never goes back to where it was. He had good days and bad days, but the White House kept it from the public. The public did not know. They saw him come out very quickly after the surgery with Nancy and look robust. Everyone thought it was OK. It was not OK. There were some very hard times in the White House because of his physical and mental situation, but he made a tremendous comeback. He rallied, and I think it's because of the Soviet Union. He was so intent on bringing them down, and that just surged him. It's a drama, and we tell you the truth. We tell you how close he actually came to having to leave the presidency. That's a very dramatic chapter, and again, most people don't know that.

Q: John Hinckley is a fascinating character. Did you figure him out, would you say?

A: Yeah, we figured him out. The man was delusional and had nothing to lose. He decided to do this violence to basically put an end to his own life. Hinckley wanted to go out in a blaze of glory to impress Jodie Foster. Crazy stuff, but he was lucid. He was found not guilty by reason of insanity, but this guy had planned this thing out pretty carefully. This wasn't some emotional thing where he got up one morning and decided to do it. We present all of the evidence that we have, and a lot of it is very harrowing.

Q: Of course there was another famous person connected to the story — you've just mentioned her. It can't have been comfortable for her, being part of all that.

A: No, but she handled it very well. A young woman at Yale, besieged by this kind of madness, and I think Ms. Foster did a very good job in not only protecting herself, but not exploiting the situation. I can't imagine the press around her. She comes off very, very well in the book.

Q: I have a feeling this might have been one of the hardest of the "Killing" books to report.

A: "Jesus" was the hardest. Martin Dugard, co-author of the books, I think is the best researcher in the world. When we decide to do a book, we outline part of it. He does the research. I, as a journalist, put a lot of questions to him: Why this? Why that? What happened here? How do we know? The thing about "Reagan" that everybody should know is that that when we were reporting it, we would not and did not use any blind sources. All of the books that have been written about Reagan in the past — not all of them, I shouldn't say that — many of them used anonymous sources. We did not. Everything in the book had to be confirmed by at least two people with their names. I would not use anything else. Let me give you an example. There was an incident while Reagan was governor (of California) where a woman accused him of adultery, but we could not independently confirm that. And we did not use it. We were very careful not to put anything in print that would disparage Ronald Reagan unless we had backup that we could point to — human beings who were there. Not hearsay. There's no hearsay in the book. And I think people will be impressed by the sourcing in this book. We used more footnotes in "Reagan" than any of the others in the series, and that was because, you know, the people are still alive. Everybody's dead with "Lincoln" and "Jesus," and most with "Patton." But there are still a lot of people around in "Reagan."

Q: Are there things you wanted to know about what happened that you couldn't find out?

A: Not really. In "Jesus," there were a couple of blind spots, and that was very, very frustrating. In "Kennedy," there was one blind spot we couldn't fill. But "Reagan" we pretty much got.

Q: Was there anything about the Reagan assassination attempt that makes it stand out among the ones you've written about in the series, other than the obvious?

A: Nothing was obvious about it. Every page is loaded with stuff that we don't believe the reader knows at all. And that's why we think it's going to be a very successful book. It's going to be a very politicized book — that's inevitable when you write about a guy like Reagan. You're going to have people who don't like him that are going to come after me, and you're going to have people who do like him, and they're going to come after me also. But we got about a dozen people who actually knew Reagan pretty well. They've all read the book, and they all come back with, hey, they liked it, it's very easy to read, fast-moving and so on. So I think it'll keep people up all night reading it. That's what we like, keeping 'em up all night.

Kevin Nance is a Chicago-based freelance journalist and photographer whose work appears in the Washington Post, USA Today, Poets & Writers Magazine and other publications. Follow him on Twitter @KevinNance1.