If they are going to change the plot, location, and characters, why do they even buy the book? It would be cheaper just to pay for an original screenplay.
Affleck will be as successful in the Ryan role as George Lazenby was in the Bond movie.
As for Clancy, he is overrated as a writer. The dialogue in his books is clearly second rate and the dopey romantic scenes he tries to interject in the books are downright embarrassing. He seems really out of touch with reality as well. For example, he's got Jack Ryan working 100+ hours a week at CIA while his wife is a full-time eye surgeon at John Hopkins Hospital who appears to put in at least 60 hours. Yet they still apparently have time to raise kids together AND have a great marriage. C'mon, get real!
But he does tell a great story and the books are technically accurate, therin lies the appeal of his books to me. I'm currently halfway through Without Remorse" and so far it is the best of the series I have read. Debt of Honor is on deck.