I bought Cryptonomicon because the back sleeve print sounded great and overall I really liked this book. The tie between WWII and a more modern day computer scientist was pretty interesting. Plus, it is rare that I can find a book that deals with wars, adventure, treasure hunting, and cryptography all at the same time. The only downside to the book was that Neal Stephenson at times seemed to talk down to his audience.
Perhaps I expect a bit too much from the audience but it seems to me the average person who is going to pick up a book about cryptographic adventures is a bit of a geek who would have some basic understanding of cryptography, algorithms, and maybe even history. Because I do have a minor base of knowledge on all of these topics I was kind of put off by the fact that Stephenson repeated some of the basics a few too many times and seemed to take a long time to explain some things that were pretty simple, in my opinion. Because of this it almost seemed like Neal was taking a chance to "brag" about how much he knows. However, even with this complaint I still recommend the book. It's kind of long, but not too bad - I've never been one to knock a book for being long (so maybe his know-it-all attitude is more bothering than I realize) - however, the story flows along pretty well.
Even if you aren't a geek, if you have any interest in treasure hunting type stories or WWII based historical fiction this would be a good novel to pick up.