This straightforward codebook is full of substitution ciphers for you to crack. Each letter in the encrypted messages replaces another letter in the alphabet—for example, the letter “X” could replace the letter “P”. It’s a simple principle that gets harder to solve depending on the snippet of code you’re given. Knowledge of the English language and an ability to spot repetitive sequences is all that is required to figure these out. Hints and answers are on the back to thwart spoilers, and there is room above each line of code to pencil in your guesses. Classic riddles and the kind of minimum-information logic problems you might remember from school fill the pages of this collection, which builds your reasoning skills. Will you be able to win gold from King Arthur, appease a hungry camel, or escape from prison? Have fun stumping your friends using the underlying principles to update the old-school scenarios to real life. The print version keeps you from impulsively clicking your way to an answer before you’re ready, but it’s also available for Kindle. Fidgeting with objects meets deep concentration in this type of deceptively simple metal puzzle. The Enigma is rated six on high IQ society Mensa’s scale of difficulty—as in most difficult. Your job: take it apart and put it back together. If you’re flummoxed and end up peeking at the solution, you’ll still learn something about mechanics—and can bequeath the struggle to a brave colleague. No matter how many hours it takes, if you solve it all by yourself, you’ll feel like a genius.
