Really!!  Buy this book!  I loved and excelled in math as a child and all through my adulthood but WHOA!! THIS BOOK!! From the very first pages, this book masterfully uses the distributive, commutative, and associative properties taught in elementary school along with really neat "tricks" to help the reader see, appreciate, and be wowed by the beautiful relationships of numbers. Arthur Benjamin reignites the fun in math and makes it wonderfully and simplistically clear how learning this aspect of math does not have to be the frightening, boring, mechanistic, drill-and-kill, painful experience that far too many of us grew up with and far too many children still have. Well written and well sequenced, each page gives simple, mind-blowing steps to boosting your mental math power!  Do a little each day and you'll impress yourself and your family and friends with you newfound math skills and confidence! :)  ENJOY!!