I got this book for Christmas and have referenced it several times for some of the most uniquely essential information. Only once, when I had to jump the car because the battery was dead, was I let down that it didn't have the instructions for hooking up the jumper cables. If you want a tiny reference about almost everything you might want to convert, measure, calculate, or guess at, or if you want to know military rank, what types of clouds there are or the area codes for New York, get this book. It is small and portable, but the print is a bit on the small side, so if you are hard of seeing, pocket it with a magnifying lens.