Angels of Vengeance by John Birmingham.
The first book was the hook for me, with the sudden disappearance of pretty much everyone inside the continental US (and implied death). Because of the timing that the author choose(2003), a lot of America's military muscle was already outside the US so that makes things slightly less catastrophic. And I kept on following things into the second book as the second order effects of the disappearance and then beginnings of reclamation of the now deserted US began (as well as the global chaos that came, nuclear war in the middle east and India/Pakistan regions).
This book picks up not too much afterward, now focusing more on the politics of the new America and her reduced role in the world. Overall it was a fairly standard action/spy novel with the unique catastrophic event background. I really only read this out of the fascination of how the author would continue to spin world events and to see what would happen to the now familiar characters. It was a fun book but I feel that this book neatly wraps up at least the characters lives in a fashion that even if there is another book, the odds of me continuing are pretty low.