I am not going to provide reviews on all of Lee Child's Jack Reacher books but suffice it to say, I love reading these. They are formulaic without being redundant. He is a good writer, the stories are engaging and easy to read. Great fun and escapism. Honestly, I think these are almost similar in nature to romance novels but appeal to both men and women. The main character is charismatic and attractive to men because of his wicked 'manly' skills and to women for the same reason. Men want to be him and women want men to be him. He is enough of a rebel and bucks the system enough to make him a bit dangerous and unpredictable but he has a military background and "does the right thing" consistently. Maybe not legal per se, but the right thing. That is the true attraction, he lives by his own code of what is right and what is wrong and helps those that need it.
Great reads for travel, can almost always find one in an airport which is how I got pulled into reading him in the first place.