content: If you have time to spare and a desire to exercise your mind in an entertaining way, then take a look at this book.It is not *just* a puzzle book, there is plenty of fact and anecdote to interest you as well. The main theme of the book is simple cryptography, as described in the works of Conan Doyle and Edgar Allen Poe. Obviously you cannot decipher relatively modern cryptograms such as those produced by the Germans in the last world war without a lot of time and a computer, but in previous times when the average person was a lot less well educated many simple codes were baffling to most readers and could maintain secrecy.Understanding how these simple cyphers work and may be "broken" is the first step to understanding modern cryptography.