If I really need a book memorized: 1. I read it 2. Reread it while highlighting the key passages. A huuge percentage of a book is non-critical - either filler

If I really need a book memorized: 1. I read it 2. Reread it while highlighting the key passages. A huuge percentage of a book is non-critical - either filler or argumentation. You read the argumentation on the first pass and make a decision, and only pick the passages you accept. 3. Read only the highlighted parts. Use spaced repetition, of course, and you can reread the key parts several times.