If you're stuck in an airport, Jack Reacher novels will kill a few hours but aren't otherwise recommended. Lee Child, the author, conceived the character as a way to make money after he was laid off from his TV job -- a dubious provenance that seems to impress some writers. The runaway success of the franchise gives a reading of the zeitgeist, at least: readers identify with a big tough guy who beats the sh*t out of people who don't ascribe to Hollywood ideals of liberal humanism. Think Billy Jack without the hippies.
Before leaving TV, Child wasn't much of a thriller reader, he admits in an introduction to one of the books, but he found a blueprint in John D. MacDonald's Travis McGee series. Like Trav, Reacher is a single, rootless, white knight for hire, except Reacher doesn't do it for money, he just stumbles into these situations where wrongs need rightin'. MacDonald wrote pulp but he had convictions, expressed in long, precocious rants about economics and politics, so engaging they caused the action momentarily to stop dead until the author ran out of gas (MacDonald even joked about this). MacDonald also had a lifelong theme, which was the dark sexual undercurrent in Ozzie and Harriett America: the McGee books first appeared in the early 1960s, around the same time as his novel The Executioners, which became the movie Cape Fear. No pulpster beat MacDonald at describing a nymph or satyr sucking someone's fortune dry.
Child has opinions, too, and they are occasionally well-expressed, but it's hard to trust such a mercenary concoction as Jack Reacher. It all seems focus-grouped. If a villain is a hunter, he doesn't just hunt deer, he lazily picks off armadillos from a truck, justifying the character's eventual humiliation. A stalker of teenage illegal aliens won't simply kill them but must also behead and partially flay them. For a child molester, nothing less than a barn full of abused victims will do.
The karma of the market played an amusing prank on Child, though. In the books Reacher is a 6 foot 5 inch, musclebound, formidable guy in his thirties. In the movie versions he is played by a diminutive egomaniac in his mid-50s.