I liked the film, and it led me to read the book. Boy, was I surprised! I have to wonder what Clancy thought of the screenplay because about the only thing they have in common is the name and a bomb that goes off...but not as or where it depicts in the film.
The book is really good, but I was continually faced with differences, so it was an interesting journey. The other reviewers have done a good job of explaining the story, so all I'll say is that you owe it to yourself, if you're a Clancy fan, to see what HE wrote instead of what the screenwriter did with it. I can assure you, you'll wonder if the screenwriter even read the book!