Write down some trigger words and form some questions as well. Really you should start activating a non-fiction book of about 200 pages not related to schoolwork and not a textbook.
Why?
Because you can PhotoRead and superread a book with nothing going in.
Have you ever read a number of pages in a book and your mind was miles away only to come back and realise that you have no idea what you were reading?
That does happen with PhotoReading as well. That's why I keep stressing it's important to have a purpose.
PhotoReading a book more than once in one sitting isn't going to improve your understanding of the topic. One PhotoReading can do that, provided you have a purpose and the other important step when you have a subject you have difficulty with, don't rush it. Let it incubate if you can and if you cannot then make sure you know what you want from the book.
Alex