I usually highlight key concepts of the chapter and rewrite chunks of text into my notebook. Typing on a computer is useless memory-wise, handwriting is more enjoyable and effective. I write small and fast by holding a ruler on the baseline.

If I enjoy a topic, I write down and rearrange chunks from different sources. If you look at the same topic from different books, it's easier to grok that knowledge.

> I read slowly and at the end of a 300 page book I might have only three key ideas that I remember, but I'm able to explain and illustrate them well.

People don't buy brochures, so the writer is driven by the publisher to write hundreds more pages. The market does not reward concise exposition. I read plenty of books with 3 pages worth of ideas and 300 fillers.