This was a fun read. Nothing about the writing was impressive. It was basically hook after hook -- which works. I mean, I couldn't stop turning the pages. The puzzles were fun too, although a bit too easy. The reader shouldn't be able to figure out all the puzzles before the cryptologist and symbologist who are the main characters.
If you are looking for a thoroughly enjoyable read, this book is for you. If you are looking for a good book on cryptology, read The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography by Simon Singh.