I found this book to be very fun. I majored in Mathematics in college and do math for a living now. I found many of the tips and "tricks" in this book to be very interesting.<br><br>My only "complaint" (its not really a complain but more of an observation, and an indication of my laziness) is that a lot of these tips/tricks require you to "un-learn" what you have learned all your life and re-learn a new way of thinking about mathematical procedures. I am particularly intrigued by the author's idea of doing math "left-to-right" and certainly do believe it has its speed merits, but it is so different than what we've all been taught in school it is hard to learn at first. With practice though you'll be zipping through calculations well enough!