A nice introductory reference book. Although one could conceivably read this over-700-page book from cover to cover (there are exercises with answers), that would be a long-term project. It's interesting, but not *that* compelling to someone who's not obsessed with codes and ciphers.
The section on codes had little interest for me but ciphers and steganography were great. The amazing ciphers used throughout history blew my mind. It was fun to try to keep up with some of them. Eventually I gave up for the DES or RSA and the 64-bit computer ones.