Before you read a book, take a blank sheet of paper and write down what you know about that subject. You can mindmap it, or you can write bullet points. Then read a chapter of that book. Now go back to that sheet and use a different color pen and fill in the gaps: what did I learn?, did I learn a different terminology?, can I connect it to what I've already read?
Before you pick up the book for the next chapter skim this sheet. It primes your brain for what you're going to read. I think that's a really effective way to not only build on the knowledge you have but to connect what you're reading to the existing knowledge. It's going to show you what you've learned because it's going to be a very visual distinction. It's going to be a different color of ink, and I think that allows you to connect to the book.
I often do this in the jacket of the book if I don't have a physical piece of paper.
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