I tried reading this book five years ago when I bought it, giving up within the first 50 pages where the author started explaining how to decrypt a ciphertext. It bored me then. I’m glad I stuck through that minor hump this time around; this is an engrossing, fascinating book about cryptography’s role in history.
Singh begins the history with Mary Queen of Scots and how she used a cipher to encrypt letters to her cohorts to plan the assasination of the Queen of England. Besides learning a lot of history, Singh describes the ciphers used in an easy to follow manner, using lots of useful examples.
For those with a computer science background, the book gets really interesting about two-thirds of the way in, when computers come into play for breaking codes developed during World War II. The history of DES, RSA and PGP are compelling, especially when you already know about those standards but didn’t know the history of them; and the author describes how all are implemented in layman terms; it is easy to follow if you know little mathematics, although it will make the programmer in you want to start coding the algorithms he describes.
The author has published a less technical version of the book: The Code Book for Young People: How to Make It, Break It, Hack It, Crack It.
I picked up this book because I read the author’s previous book, Fermat’s Enigma, which is a lot more technical than The Code Book, but it’s an interesting tale nevertheless; non-technical readers can skip the meaningless stuff. That book is about how was solved after almost 400 years.