Those walking into "Jack Reacher" with little knowledge of author Lee Child's popular book series are probably asking themselves "Who is Jack Reacher?" Moviegoers walking out of Tom Cruise's latest action romp, on the other hand, are probably asking themselves "What is `Jack Reacher'?" Because after 130 minutes, it's hard to walk out of the theater knowing what kind of movie "Jack Reacher" intends to be.