I read Code Breaking: A History and Exploration by Rudolf Kippenhahn. It was pretty decent. I came away convinced that Kryptos is truly a pencil/paper coded system. All of the analog ciphering methods have ways to solve them with or without keywords therefore it’s basically necessary to identify the method used and then follow the procedures to decipher the plaintext. Classically, it would appear that substitution and transposition (in multitudinous incarnations) ruled the day when we had to do it by hand. This makes sense as all you really can do is change what the message is or change the order.
Personally, I think steganography has inspired the greatest interest in me. Kryptos in some ways is not applicable because we know it’s ciphered which removes the chief strength of steganography. There are some hidden elements, sure, but true steganography means hiding something that a non-recipient doesn’t know is even there.
This books was decent but I was left wanting more of a cryptanalysis outlook which would be useful for Kryptos. For anyone just looking to brush up on code/cipher history, this is a decent book. It’s also probably fairly interchangeable with a number of other books that attempt to give the same information.
I would recommend this book for someone who hasn’t read something similar or for anyone just getting started on codes and ciphers.