I know what you mean. However this wasn't the case when I listened to the commentary on Sum of All Fears. Tom Clancy was commentating with the director, and several times Clancy talked about how the movie could have been much better and how the plot didn't stick to the plot in the book at all, and this lead to a couple of seemingly awkward moments in the commentary.

I agree with Clancy though -- his books are always great, but that movie sucked. It sucked almost as much as The Hunt for Red October. Patriot Games and Clear And Present Danger are the only good Clancy movies.