While it may seem self-evident, authors must make conscious decisions about which people to put in a book, and it is often the most crucial moment of their career when the central figure of the story is invented. Clearly, it becomes an even more monumental choice if the protagonist is destined to be a series character.

For some authors, the whole process seems to be almost accidental. The hero of Patricia Cornwell’s first book, “Postmortem,” was not intended to be Kay Scarpetta but homicide Captain Pete Marino, until a wise editor suggested that the forensic pathologist would make a better choice. Robert Crais’s Elvis Cole was planned to have a single appearance but remained so persistently in the author’s mind that he has now been a major presence for 20 years.

For Lee Child, however, the creation of Jack Reacher, the hero of “Bad Luck and Trouble” (Delacorte, 377 pages, $26), had nothing to do with accident or serendipity. The process was carefully thought out because the author knew exactly whom he wanted to spend time with and whom he understood well enough to write about convincingly.

In a recently published profile of Reacher, Mr. Child wrote that “Character is king. There are probably fewer than six books each century remembered specifically for their plots. People remember characters. Same with television. Who remembers the Lone Ranger? Everybody. Who remembers any actual Lone Ranger storylines. Nobody.”

He decided that his character had to carry the load, and he wanted him to be different from other series characters. “If you can see the bandwagon,” he said, “it’s too late to get on.” Mr. Child understood that most successful series, as well as many that were just beginning, included heroes who were part of a cast on location. The environment was fixed and important (Spenser’s Boston, Bosch’s Los Angeles, Morse’s Oxford), and they had partners, pets, favorite hangouts, family, and friends, etc.

None of these elements pertain to Reacher. Like many of the great detectives of the past, Mr. Child’s character has nobility, metaphorically connecting him to Raymond Chandler’s paradigm of the knight errant. He has a strong moral code, though it may differ somewhat from written law. A cross between Mike Hammer and James Bond, he is fearless, competent, and honorable. He is also relentless and violent, utterly lacking in compunction about brutalizing or killing a villain. Add the fact that he is huge (six feet, five inches, 250 pounds of muscle, and described in an earlier book, “Tripwire,” as resembling “a condom filled with walnuts”), and he becomes a highly dangerous foe.

In “Bad Luck and Trouble,” the former military policeman receives a coded message from a member of his old team of special investigators. One of the team has been killed — thrown from a helicopter high above the California desert — and others have gone missing. It becomes Reacher’s job to reunite the old unit and take on a formidable enemy.

Essentially a drifter and a loner, Reacher has deliberately removed himself from society, its conventions and its obligations. He is, nonetheless, devoted to his old colleagues and will risk everything for them, with nothing to gain except vengeance and the moral requirement of loyalty.

An enormous and powerful force is arrayed against Reacher and his team, and they find themselves in apparently hopeless positions more than once in this non-stop, action-filled thriller. They have confidence in each other in terms of loyalty, courage, and competence. Of his team, Reacher thought he “could send them to Atlanta and they would come back with the Coke recipe.”

In a particularly dicey moment, they assess their situation:

“Two against seven or more.”

“No time.”

“No element of surprise.”

“A fortified position with no way in.”

“A hopeless situation.”

“‘We’re good to go,’ Reacher said.”

As with all the books in this wonderfully addictive series, a lot happens. You will search in vain for long descriptive passage extolling the natural beauty of a sun setting over a mountaintop. There is precious little introspection. It would be superfluous. Reacher knows what is right and what is not. The only issue then becomes how to act most effectively. After all, did John Wayne worry about whether he was doing the honorable thing?

When I despair that it has become unfashionable, even a subject of ridicule, to suggest that someone is an American hero, I console myself with the knowledge that Lee Child didn’t think so when he gave us Jack Reacher. And, as book after book climbs higher on the bestseller lists, it is clear that a lot of other people don’t think so, either.

Mr. Penzler is the proprietor of the Mysterious Bookshop in Manhattan and the series editor of the annual “Best American Mystery Stories.” He can be reached at otto penzler@mysteriousbookshop.com.