I first read this book when I was about 14, around 1978. There is a concentration exercise using a number 2 pencil that I still remember to this day. This book approaches E.S.P. from the standpoint of accessing the untapped capabilities of our physical brain. Although the theme is generally metaphysical, I found the book to be very scientific, practical and sensible. I highly recommend this book not only to those interested in E.S.P. but also to those interested in enhancing their more traditional mental abilities such as memory, focus and attitude.