I think the easiest way would be with a VPP. I could have each book just contain a selection of powers and a side effect of the VPP being that they can only use those powers unless they swap out.
This was how the concept was relayed to me:
"Each book would have some sort of a theme, and the powers available within would vary. So, for instance, I could have a book inspired by a desert traveller which would grant me some skill bonuses, survival powers and maybe some fire powers. Another one could be about archeology and give me a lot more skill bonuses. Maybe a warrior manual would give me martial arts."
To keep it balanced with the other characters, I don't think I'd allow more than a single book's powers to be accessible at once. I'd also probably have it so some in-game time would need to pass to swap them out, making choosing the one you want to use have some weight instead of being able to continually swap around powers in combat. It will also make my life easier as the GM!