Lolu,
When you're talking about something like textbooks, which I imagine is what you're looking at when referring to chemistry and German, the best way to go through each of those is to treat each chapter as an entirely separate book within itself during the activation process. This means spending as much time on a single chapter as you might an entire book elsewhere. Because often times in a school textbook, each chapter presents you with an equivalent amount of information that you'll find elsewhere in entire books - spend half hour activation passes until the entire mass of concepts 'gel.'
Go through each and individual chapter with multiple passes. For really complex, structured information that is very fact driven and in a dense text with concentrated information - mind mapping everything out usually helps, or at least writing down the separate concepts and how they all inner relate to each other.
-Scott Lee
