learning and memory depend crucially on rehearsal.
After you’ve read the book, rehearse what you’ve learned. Quiz yourself on its contents. Argue with the author. Imagine how you would defend the author’s position in your own writing.
The best forms of rehearsal use multiple modes of thinking. Don’t just contemplate privately. Instead, talk about the book with others. Bring it up in classes. Write about it. Visualize anything that can be visualized about its contents.
Using different modes of thought helps fix your memory and integrate it into the rest of your knowledge.