Check page 25 of the PhotoReading book. Next to Einstein jogging. Read all of it not just the italics.
The main thing is purpose is how and why you are setting your sails. It is one of the things you need to do to reach a goal or destination in your life.
In a way PhotoReading is collecting tools to use for various jobs, duties or things you want to build for your life. When you buy a tool(read and activate a book) imagine explaining why you are spending money on yet another tool to your significant other. Tell them why you are buying it and how it will help you reach your goal. (why are you "spending" time with this author. How is what they say going to help you on the path toward your goal. What do you plan to learn from this person who wrote the book?) How is what this person has to say going to change your life for the better? What possible benefits can you get from the book.
When you PhotoRead a book as part of the PhotoRead only exercise get into the habit of saying the opening and closing affirmations. Then when you have a purpose your mind will zero in to the information for activation.
There is no one purpose fit all model. After your intial activation your purpose might change. You might discover the author has some facinating information not metioned on the cover of the book but it applies not to e.g.your goal of getting into an exercise routine but it is a motivationalsection that gives you the idea that you can use on the late arriving employee. Your purpose for the book has now changed in a big way. The original purpose may still be valid but the second purpose might prove even more valuable.
Alex