Back Blast by Mark Greaney

Let me summarize the skills of Court Gentry, the black ops assassin otherwise known as the Gray Man, from Back Blast, the latest novel by Mark Gearney:
“He can fly planes, scuba, rappel, fast rope, and free climb. He’s a master in the Israeli martial art of Krav Maga, and he’s the best close-quarters battle tactician to ever serve in SAD. He’s been to jump school, sniper school, advanced surveillance school, explosive breaching school, SERE school.”
Since he’s been on the run for the past 5 years, banished by an infectious cabal in the highest reaches of the US government, Gentry decides to return to America to find out who’s behind it. When they learn he’s back in DC, everyone sleeps with one eye open.
This is a great series. As always, I suggest starting with the first book in the series, The Gray Man.