Steven Kirk is an agent with the CIA.
Technically, for most of the two-book series, he is no longer an agent. Even more technically, for all of the first book, he is not even Steven Kirk. He had, to escape those looking for him because of secrets he knew that many higher-ups did not want him to keep, changed his name to Scott Craik. At the end of the book, he threw that name away and took the handle Steven Cramer. At the beginning of the second book, after suffering a terrible loss, he discarded this second alias as well and reverted to his original name as he realized that running would never end.
Kirk is in his mid-30s as the series begins. He may not be as young as he was when he first joined the Agency but even those not trained in close observations have no trouble seeing that he is in top physical shape, easily able to take care of himself. Mentally, he is just a sharp and can spot trouble and troublemakers long before anything happens. Where he is clearly showing signs of age, though, is in his spirit for he is bone-tired of the things he has had to do in the CIA and wanting a break. He just did not want to take the break like he did, hiding from his past.
Even though the CIA and the actions that Kirk took as an agent during the Grenada invasion during the early 80s play an important part in the first book, the adventure is really a tale of a former operative wanting no more violence coming into contact with a local crime boss who is used to pushing others around. Kirk shows he does not get pushed very easily and can push back a lot harder than his opponents realize.
The second adventure is far more of an espionage thriller when Kirk, out for revenge and not planning to give up his search for those who hurt him and his, still has to take on a case to stop suspected terrorists from killing thousands of innocents.
In both books, regardless of the enemy, Kirk shows he should not be messed with. He invariably is but he shows them how wrong they were.