My lovely girlfriend just finished reading Dan Browns Digital Fortress and handed it over to me. I finished it in two nights, just as his other books, and I think this book is at least as good as The Da Vinci Code.
Unfortunately it's not as detailed on the cryptology part as I would have liked, but at least he succeeds with a bit of name dropping. I remember Diffie-Hellman and ElGamal being mentioned, along with some other cryptology terms. The classic Caesar cipher was described more in detail as it's easy for anyone to understand how it works.
The story is basically the same as his other books, shy academic guy is forced to play detective instead of solving the problems he has with his beautiful and clever girlfriend. The plot is based around the search for the key to an "unbreakable" code. The NSA can't break it, and send the professor David Becker to Spain to get it back. Meanwhile, things are not going according to the plan back at the NSA Crypto headquarters...
It's a fun story and very fast paced as usually. Everyone is lying to everyone and it's not obvious right away who is fooling who. Feels like a perfect book to bring for a lazy summer day, except that you'll finish it in a few hours of reading.