If you're still learning to photoread pick a subject other than physics. The variables in that subject alone are complicated enough and if you haven't got a hang of photoreading you've chosen a subject that will keep you on edge when it comes to activation.
First books should be non fiction books of a subject that interest you that you may already know something about. Self help, how to and management type skills books are a good place to start.
Also consider your purpose. Ehen you say "because you have to understand every detail" it becomes apparent you haven't really considered your own purpose for activating those books.
Alex
