If you only read one Clancy novel, it should be Red October Rising. It is stand alone from his universe the other books are in. Worth it for expressing the tension the world was under during the Cold War.
Some of “his” later books were in fact by other authors: his name prominent on the front cover, actual authors name in smaller print. They were decent reads as well, albeit formulaic. Some of All Fears and Debt of Honor were a couple more I found real page turners.