Princeton University Press (2017) RRP US$29.95

THIS IS A FASCINATING TOUR of the mathematics behind cryptography, showing how its principles underpin the ways that different codes and ciphers operate. Holden starts with “simple” substitution ciphers and goes on to explore polyalphabetic substitution ciphers and transposition ciphers. While it’s all about maths, the book is accessible – basic high school algebra is all that’s needed to understand and enjoy it.