Maybe it is the best practical book:School of Out-of-Body Travel
A Practical Guidebook.
From website http://obe4u.com/
This guidebook is the result of ten years of extremely active personal practice and study of the out-of-body phenomenon(the phase), coupled with having successfully taught it to thousands of people. I know all of the obstacles and problems that are usually run into when getting to know this phenomenon, and have tried to protect future practitioners from them in this book.
This guidebook was not created for those who prefer light, empty reading. It is for those who would like to learn something. It contains no speculations or stories, only dry, hard facts and techniques in combination with a completely pragmatic approach and clear procedures for action. They have all been successfully verified by a vast number of practitioners that often had no prior experience. In order to achieve the same result, it is only necessary to read through each section thoroughly and complete the assignments.
The book is beneficial not only for beginners, but also for those who already know what it feels like to have an out-of-body encounter and have a certain amount of experience, as this guidebook is devoted not only to entering the state, but also equally dedicated to controlling it.
Contrary to popular opinion, there is nothing difficult about this phenomenon if one tries to attain it with regular and right effort. On average, results are reached in less than a week if attempts are made every day. More often than not, the techniques work in literally a couple of attempts.
OOBE Research Center