Less military and techno-detail, and a less turgid writer than Clancy. Cussler novels zip right along. Also, I like the characters better. Try the “Oregon” series, those are my favorites.
I like thrillers by the author Douglas Boyd. He wrote “The Fiddler and the Ferret”, and other good ones. He is not as well known as he should be, but his books are good stuff. Very good background about the intelligence agencies and how they work.