The ending is pretty unsatisfying. For the last sixty pages the author lost the thread, and riffed on a lot of nonsense. I remember the movie's ending seemed kind of tacked on too.
Wrote himself into a corner, he did.
Incidentally, since I mentioned Jack Reacher, I looked on PPV and there's a TV series on Amazon Prime (not the horribly miscast Reacher movie with Tom Cruise). The TV show at least has a Reacher that resembles the book.
But it's laughably bad homoerotic cartoonish stuff, with a hero who beats bad guys to a pulp with his fists while remaining immune to bullets and metal bars. He's built like a Tom of Finland model, has no interest in girls, and spends a lot of time flexing in front of a mirror. Spank fodder for gays.
Not that there's anything wrong with that.