This book changed the way I think and go about my day-to-day studying and working.  The author does such a wonderful job of introducing advanced mental math techniques in a fun, easy-to-understand manner.  I specifically bought the book to help me during my consulting case interviews, and it helped me tremendously!  During those interviews, you are not allowed to have a calculator, so I relied heavily on the techniques that the author taught me, and they paid off!  I recommend this book to anyone that wants to learn how to live life without dependence on a calculator, or simply wants to make their life easier!