In the new Expanded Edition from No Starch Press, released in the U.S. on September 19, 2023, you can find:

• All the latest details on previously unsolved codes that have been solved since our first edition, such as:
  
  • The Zodiac Killer’s Z340 message, solved after 50 years by an international trio of amateur cryptologists;
  • The thrilling discovery by amateur codebreaking sleuths of scores of encrypted letters written by Mary, Queen of Scots, where the documents had been misfiled in a corner of the Bibliothèque Nationale de France;
• New information on two different sculptures on either side of the equator:
  
  • Kryptos in the Northern Hemisphere, and
  • The Australian NKRYPT in the Southern.
• Reaching back to the nineteenth century, we’ve added more about the still-unsolved Furlong postcard (which you can see faintly on the front cover of the new edition), and
• The encrypted Collinson ads in the London Times from 1850-1855, and their exciting connection with the lost Franklin Expedition.
• We’ve also provided updates on:
  
  • The recently exhumed Somerton Man in Australia;
  • The message from a World War II carrier pigeon that was found in a chimney in 1982;
  • Edward Elgar’s Dorabella Cipher of 1897; and
  • The Chinese Gold Bars, from our conversation with Peter Bisno, Esq., in December 2020.

Other additions include:

• A nomenclator message sent by Charles I of England that we found in the archives;
• Drawing from our new article in the academic journal Cryptologia, “How We Set New World Records in Breaking Playfair Ciphertexts,” we’ve added more information about the hot cryptanalytic techniques of hill climbing and simulated annealing, and how they are being used to solve older ciphers left and right.
• We’ve also fixed several errors that crept into the first edition. Thank you to all our eagle-eyed readers!
• An appendix with a Morse code table (we were astonished to learn we missed that in the 2020 edition!)
• A new section on the Voynich manuscript that shows the results of our comparing its traits with similar encrypted books from the last 600 years;
• Many new references;
• An updated metapuzzle (with a fresh hint or two); and
• An expanded reading list of additional titles of use to codebreakers, including several new biographies of Elizebeth Friedman.
• And last but not least, an updated list of Acknowledgments, thanking everyone that has helped us along the way!