Mike Black is an assassin for the Alliance.
He is also the "author" of a fair number of fairly successful action novels.
Regarding the quotes on that last statement, it is a pseudonym of Michael Stryker on those fantasy adventure tales but it is Mike Black's bank account the royalties end up in as the "real" name of the author but he has not written any of them. The author gig is a cover to explain his income, in the rare case it is ever asked about, and for his frequent disappearances - research for the next book and book tours for the previous one will suffice in any casual inquisitor's mind. He might wonder at times who the ghost writer was but asking the Alliance would lead to complications and that is something he does not want - ever.
Black "lived by two simple rules. No witnesses. No complications."
Which sort of brings us back to the assassin gig.
He may be a paid killer for the government; that is, the Alliance may be secretly part of one of the many alphabet organizations that exist in the American intelligence community. He has long thought that but never taken the time to research it. He has pondered often over the 18 years he has been doing what he does how the Alliance did many of the things like they do, but finding out the truth would inevitably lead to complications...
One other minor nit to pick - Mike Black is not his real name, either; it is just what the Alliance has chosen to call him. He has not used his given name in years.
Black explains at one point in the first adventure how he became the killer he has been for nearly two decades. "I was a tough kid. Although I didn't get into too much trouble, I was close enough to taste it. For the most part, it was a normal life. No, I didn't become a hitman because I was abused or anything. After I got out of school, I joined the service. All of the government agencies keep an eye on people who serve. They look for certain personality types or those with special skills. If you check off the right boxes, they find a way to contact you. I must have fit one of the molds they were looking for." He adds, when asked if he was talking specifically about the CIA, "Not just them. The entire alphabet is always on the hunt for people with likeminded ideas. While I can't prove it, I believe the company I work for is affiliated with one or more of the intelligence agencies. It makes sense given the resources at their disposal."
As the adventures of Black proceed, we are able to watch him become involved with not one but two different women, both quit a bit different for the other but both adding something to his life that he was surprised he had been missing. Another thing that surprised him was that he was very welcoming of both even though they would both create complications.