A bit dated, but still lots of useful information. Such as: What do those bars in UPCs REALLY mean? (No, it's not the Devil or 666.) How is octane measured? How is relative humidity measured?
It's too bad this book is now well out of date (ca. 1989) because it's a marvelous compendium of insight and wisdom on the mysterious numbers and codes associated with everything from tire sizes to UPC codes. I'd definitely consider this as an essential reference! And it's fun to read.