A nice trip back in time to Jack Reacher as an MP. Get to meet his family. Although I figured out one clue right away, Child still managed to throw in surprises at the end.
Amazing scene with Reacher and his brother taking leave of their dying mother in Paris:

Then she revisited another old family ritual. She did something she had done ten thousand times before, all through our lives, since we were first old enough to have individuality of our own. She stuggled up out of her chair and stepped over and put her hands on Joe's shoulders, from behind. Then she bent and kissed his cheek.
"What don't you need to do?" she asked him.
He didn't answer. He never did. Our silence was part of the ritual.
"You don't need to solve the all the world's problems, Joe. Only some of them. There are enough to go around."
She kissed his cheek again Then she kept one hand on the back of his chair and reached out with the other and moved herself over behind me. I could hear her ragged breathing. Then she kissed my cheek. Then like she used to all those years before she put her hands on my shoulders. Measured them, side to side. She was a small woman, fascinated by the way her baby had grown into a giant.
"You've got the strength of two normal boys," she said.
Then came my own personal question.
"What are you going to do with this strength?" she asked me.
I didn't answer. I never did.
"You're going to do the right thing," she said.
Then she bent down and kissed me on the cheek again.

I think this exchange is the key to Reacher's ability to lead a nomadic life. When your mother has known you so well, and been your true home, you don't need any other home. It's enough to carry the memory of that love and understanding with you wherever you go.