Almost everything about this book is great. Simon Singh is a wonderful story teller. He manages to get through the science without dumbing it down. From ancient monoalphabetic codes to quantum cryptography, the book is an enthralling read. Why "almost"? At this point the book is over 20 years old, and things move fast in the computer cryptography world. For example the use of DES has long been discouraged. But that's not the book's fault of course.