This is a toughy for me, but I've read 'The Hunt for Red October' twice already and it still is great.
So I'd say The Hunt for Red October...
[ame=http://www.amazon.com/Hunt-Red-October-Jack-Ryan/dp/0425133516/ref=sr_1_1?ie=UTF8&s=books&qid=1266274309&sr=1-1]Amazon.com: The Hunt for Red October (Jack Ryan) (9780425133514): Tom Clancy: Books[/ame]
So I'd say The Hunt for Red October...
[ame=http://www.amazon.com/Hunt-Red-October-Jack-Ryan/dp/0425133516/ref=sr_1_1?ie=UTF8&s=books&qid=1266274309&sr=1-1]Amazon.com: The Hunt for Red October (Jack Ryan) (9780425133514): Tom Clancy: Books[/ame]