I ❤️ these book but have sadly read them all now. I would like to recommend one to a friend who hasn't read them.
Unfortunately they're all in a mush in my brain and, while I now some are better than others, I can't remember particular ones.
I suppose I could suggest starting with the 1st one, but I don't think it was one of the best.
Fwiw, I do think the ones where reacher is referred to in the 3rd person singular are better, and I am not keen on the ones where he's joined by previous army friends.