I found after fully activating around 20 books. You need to follow the entire system though until the book gels and your purpose is met. It depends on your purpose on how long the book will take too. I'm right now going through a logic text and doing the exercises it will take at least 1/3 of the time because it is highly analytical work. So start out with non fiction how to books 200-300 pages. At least that is what I did after fighting the system and trying to make it work as a shortcut for over a year.
