A walk through combinatorics (Fourth Edition) by Miklos Bona, pp. 593, PS91 (hard) ISBN 978 9 81314 884 0, World Scientific (2017)
opportunity of referring to the decryption described in detail in Dorothy L. Sayers' Have His Carcase, which is where many will have first encountered Playfair. Later chapters involve a number of cipher messages that have been written by criminals or as self publicising challenges to the rest of the world, and I must admit to a sense of distaste in giving these things more publicity. The final chapter describes RSA and associated challenges. The writing is straightforward, restrained and user friendly, with plenty of clear illustrations of the actual working of ciphers and what has come out of plausible attempts to decrypt the messages, although there is not very much actual mathematics. As usual from this source, the book is beautifully produced and very modestly priced, especially considering its length. A book for those who are fascinated by codes in general, I think, rather than by any specifically mathematical aspects.
The Mathematical Gazette