Millions to Measure by David M Schwartz

Take a trip with Marvelosissimo the Mathematical Magician in his hot air balloon!  In this book, we travel back into time to discover the origins of measurements, first in feet and pounds, following that into standardization of the foot, expansion into large units and finally introducing the metric system.  The book ends with a comparison of the two systems, and comments that the US will likely eventually switch over to metric to join the rest of the world.  :)  This is one of those great resources that is very educational, packed with information and still fun enough that my 1st grader understood the material and commented, "That was a great story!"  Perfect for some living math into your kid's day.  A little bit of an appendix in the back expands on the information presented in a more detailed and factual manner for parent or educator if you want to expand the lesson.  The book does not cover Celsius versus Fahrenheit at all, but the appendix covers it some if you want to present it also as an expansion of the topic. 

Illustrations are cartoony with comments bubbles, a style most kids like.  And who could dislike "Hercules the Huggable Hippo"?  Excellent book for fun or teaching.

Note, this is a series.  We will be looking up the others in the series, as they too look great for living books in our elementary math.