But he hasn't written anything new since the mid-90s.
After Red October and Red Storm Rising, everything was written using a formula.
The exception, I think, being Rainbow Six.
And after that point, with the Clancy name entering the video game world (classic but niche Microprose games not withstanding) he took a step back.
Just about everything with his name on it, including books in his main novel series, was ghost-written from his notes and formula and he just slapped his name on it to get his percentage of the take.
The man is significant in that he has a minor media empire with his name on it, but he stopped being a writer a long time ago. There are people almost old enough to vote who didn't live in a time when he actually wrote.