Whenever you take notes from any book try these three questions

1. How I can use this? 
2. Why I must use this?
3. When I'll use this?

When you start questioning this, you will be more clear why you are reading the text. That will help to involve in the reading and the more you involve in the reading more you can remember. Try to make notes in your own words.

Whenever you complete a chapter or a book try to create a mind map. A mind map is just doodling in your note pad about what ideas you got from this chapter or the book, what are key ideas need to be remembered. I'll help you in the next step.

We forget almost 70% of the things after 24 hours. So we need a revision plan. Whenever we revise something it takes less time than the previous. According to the study, after reading something, we must revise that within 24 hours then within a week, then within 1 month after that whenever you need it. If you revise the thing within the specified time then the thing will go to your long-term memory.

The best way to remember something is just to share the knowledge that you have learned, teach them. When you share the experience you have learned, the experience repeats itself in your mind and it saves your long-term memory. Just like I'm sharing these ideas with you people so that I can remember them better and you also learn something new.

Teaching is one of the best to master a topic, which is part of the Feynman technique.