Like most boys growing up in era of the cold war and the original James Bond movies, I was part of a club where we created our own secret codes. It was great fun and we were constantly improving our codes to thwart the efforts of others who wanted to read those "important" messages. Had this book been available back then, we would have devoured it. Written at the level of a middle school student, the basic codes are thoroughly covered, yet not at a level beyond the child of the early teen years. No mathematics beyond simple arithmetic is used.As befits the original publication date of 1975, computers are not part of the codes, which I found to be an attractive feature. Writing simple codes is an exercise in thought, a process that computers sometimes interfere with. This is a book that can be read for enjoyment, and it can also be used as a book for class work designed to be fun. It should be in every middle school library.