Greaney’s fifth Gray Man thriller, Back Blast, focuses on the exploits of ex-CIA operative Court Gentry. Since the death of Tom Clancy in 2013, Greaney has also written Jack Ryan novels, most recently Tom Clancy: Commander in Chief (Putnam, Dec.).

You collaborated with Tom Clancy, starting with 2011’s Locked On. How did that happen?

Tom Clancy and I had the same editor at Penguin, Tom Colgan. When Tom Clancy was looking for a new coauthor, Tom Colgan reached out to me. I had only been a published author for two years at the time, so I was astonished, to put it mildly.

Do you work on a Clancy and a Gray Man simultaneously?

My brain would probably explode if I bounced around day to day from one to the other. I always finish one before starting on the next. It’s a little difficult at times, especially when I begin a new book, but the two series are distinct enough so it’s not too much trouble.

How are the two distinct?

Tom Clancy novels tell stories that are wider in scope. They are more geopolitically oriented; they’ll take you from the Oval Office to a back alley in Vietnam, or from a millionaire’s luxury yacht in the Virgin Islands to a Russian submarine below the Barents Sea. The Gray Man novels are somewhat edgier style-wise, both in the delivery and the subject matter and a bit more street level in their scope.

Do you enjoy putting yourself into Clancy’s head?

I really do! I don’t try to write in some Tom Clancy style—that seems disingenuous, and I honestly have no idea how to do that. I told myself from the beginning that I just had to be honest to the characters as Tom created them and research every facet of the novels as much as possible, because that was such a Clancy hallmark.

Would you consider doing other series whose authors are no longer with us? How about taking a crack at James Bond?

I’ve honestly never thought about that. I’ve been a fan of the Bond books since my 20s, and I think I could pull off a gritty version that goes deep into the psychology of a government-sanctioned assassin. I’d want it rooted in realism, much like both my Clancy and Gray Man series, but with just enough fantasy to pay homage to the Ian Fleming books. To do it right, I’d require a lot of time in the U.K. to get the atmospherics down, and of course I’ll need to expense an Aston Martin and an exploding Rolex for research purposes. I’m liking this idea—I’d better go call my agent.