Blowback - Brad Thor

Blowback is the fourth novel in the Scot Harvath series. The world is so dangerously to a Sunni Caliphate.

Scot was working for DHS. Now he's sort of on his own, since there's a senator looking for his scalp, along with most of the word media. Even when Scot's on his own he's still fighting for America. This time against a plot that's going to use a weapon that's thousands of years old to kill most of the non-Muslims in the world. Very highly recommended.