Just finished, and it is a great novel, perhaps near the top of his work. Swagger is now "retired", in his early 70s, working on his 3rd hip replacement, and yet Hunter crafts a role for him that fits, and uses all of Swagger's skillset.
 
Short blurb from the jacket cover of the book:
"Master sniper Bob Lee Swagger must confront the one enemy he never thought he'd encounter: his equal."
 
bobleeswagger (you'll get this when you read it) makes a superlative accounting of himself (as we've come to expect). A very enjoyable read.

Looking forward to this one, I will buy it when it comes out on paperback.