Awesome series.
After finishing up on Mitch Rapp to date, I branched out into other similar series and found a few good ones.
Long since finished on Dirk Pitt and Jack Reacher, both long standing terrific series that are different in style and scope than Rapp, but if you can buy the intricacies of the characters, the series can give you many months of enjoyment.
The Orphan X series is a winner. Finishing that, I jumped right into the Will Robie series by David Baldacci. That was also a 5 book series which is very close in style to the Smoak books.
Now on to the Scot Harvath series by Brad Thor. Very close cousin of the style and plotlines of Rapp, Smoak, and Robie. Eacb of the characters has similar traits and outlooks, but different skill sets. Very fun.