The Detachment is the 7th book in the John Rain series. I usually like to read series books in order, but I got this one for a low price so I started in the middle.
John Rain is a professional assassin. In this book, he is hired to kill two people who, purportedly, are plotting a coup against the government of the USA. His employer is Scott Horton, a colonel who specializes in "black ops". But ... there are twists and twists and more twists.
Although Rain usually works alone, this time he is leading a team of four - and there are lots of interpersonal problems. And it's soon unclear whether the coup attempt is real. Then there are terrorist attacks.
I won't say it's great literature, but it kept me turning the pages, which a thriller should do. I'll be looking for the earlier books in the series.