This is a superb text. It is both comprehensive and accessible, which is an infrequent combination. It introduces the reader to cryptography and cryptanalysis, subsets of the broader field of cryptology, which might be loosely referred to as the study of codes.

The book begins with an overview of the impact of cryptology on today’s world, providing examples of numerous critical points in history at which codes or ciphers played a decisive role, either through the successful use of cryptography, or, more frequently, through its failure in the face of cryptanalysis. The eponymous Mary, Queen of Scots, is one such example. The breaking of Enigma in World War II is another.

The text describes and defines cryptography, the use of algorithms to convey messages in a manner (purportedly) indiscernible to any not possessing a specific key, providing numerous examples and illustrations along the way. It also provides a clear, though brief, introduction to cryptanalysis, the breaking of such messages without a key, to the derivation of keys and algorithms, and to how such information can be used to forge messages. While this text doesn’t provide the same mathematical depth as Schneier’s or Stalling’s, it does provide a strong introduction in an extremely accessible form, and avoids intimidating the nonacademic with excessive mathematics.

Singh is an accomplished author, having previously written Fermat’s Last Theorem [1], the first bestseller on mathematics to be published in the United Kingdom. He then tackled encryption with this book, which was later adapted for a five-part British television series. The series won the Main Prize in the 2001 Vega Awards, recognizing the most effective examples of science-related broadcasting in the past year.

Singh’s capacity for storytelling is evident in this book, which serves as an excellent history of cryptology for the layperson, an introduction to the mathematics behind cryptography and cryptanalysis for the inquisitive, and an enjoyable read for any who may be curious about the art and science of codes. While it won’t enable casual readers to design effective codes, nor to break them, it will enable them to understand the processes and goals behind this critical, yet hidden branch of inquiry. For these reasons, it is highly recommended to all readers.