Activation in "layers" simply means going over the book more than one time, Helenora.
You'll still remember information you previously activated, but you will be getting more. Everytime you reread something, you learn something new.

Stork,
How do you know that you normally read a book successfully? You don't really think about that, you just know the information in it. When you have an understanding of the book and can discuss it's content with someone, you have successfully photoread the book.

Your session is on the right track if you do that ^^^ often.