I remember reading in Entertainment Weekly or one of those kinds of magazines that they paid John Milius something like $1,000,000 to write a "compromise" screenplay that more closely followed the plot of the book, but that had reasonable screen time early in the movie for Harrison Ford. They ditched it and filmed what was released in the theaters. If I had to rank my top 5, it'd probably go: 1. Without Remorse 2. Clear and Present Danger 3. Debt of Honor 4. Executive Orders (because it picks up right where Debt of Honor left off) 5. Tie between The Hunt for Red October and The Sum of All Fears
Hurm. Top five Clancy books? 5 - Cardinal of the Kremlin 4 - Patriot Games 3 - Hunt for Red October 2 - Red Storm Rising 1 - The Sum of All Fears
I re-read CotK maybe 10-15 years after its initial release, and I honestly didn't think it had aged that well. Had a similar experience, to a lesser degree, with PG.
