The author of this book was party to a cryptological society, still around, founded in the early 1920's which made, and solved, cryptograms as a hobby just as people 'do' crossword puzzles.
All crypto can, loosely, be divided into the sort used by governments, banks, international drug traffickers, and those using digital communications and that type of crypto used by people who just don't want secretaries, nosey people or their teacher peeking into their lives.
This book will most likely cover all the later groups crypto needs. I have used it, almost exclusively, for 30 years, where fast and short communication was needed to a known recipient with a decryption 'key'.
This book uses complex English and print which is uncomfortably small. There are some 'gems' of obscure information in this book as, by example, a frequency list which identifies the final letter of 10,000 typical words in Portuguese ... O.K. ... nothing I suspect that one could not 'figure out' but nothing I suspect that one ever would.
While a trained crypto analyst might unravel these in short order they are impenetrable to most secretaries, nosey folks and schoolteachers.