Jack Reacher is the lone-wolf thriller distilled to its purest form - a wandering tough guy who walks into trouble and punches his way out. These series scratch the same itch with their own twists on the formula.
Both protagonists are supremely competent loners with mysterious pasts and a personal code. Hurwitz writes fight scenes and tactical detail that rival Child's best.
Both feature an unstoppable protagonist operating outside the system. Greaney's military and intelligence detail is meticulous, and the body count is high.
Both protagonists are lethal, patriotic, and willing to bend rules. Flynn writes with insider knowledge of Washington power dynamics that adds real tension.
Both feature tough protagonists who protect the vulnerable. Crais brings more humor and a Southern California atmosphere, but the bones are the same - justice delivered personally.
Both protagonists are patriotic tough guys who solve problems with brains and fists. Thor layers in more international politics and conspiracy than Child typically does.