"'Tis the good reader that makes the good book; in every book he finds passages which seem to be confidences or sides hidden from all else and unmistakably meant for his ear; the profit of books is according to the sensibility of the reader; the profound thought or passion sleeps as in a mine, until it is discovered by an equal mind and heart."
--Ralph Waldo Emerson
I love this quote. I often read with a small notebook close by so that I can write down thoughts or ideas that spring from my reading. Sometimes I will be struck by a quote and want to record it so that I can read it again later. Other times, a situation in a book will remind me of something similar that I have experienced. I like to summarize my thoughts and reflect on books when I finish them.
The really wonderful and great thing about learning through books is that not every person comes away with the same message. So the hidden treasures of knowledge are not the same for each person, or even the same each time a great book is read. There are some books that seem to speak to me over and over again. I have found writing down my thoughts to be helpful in preserving the insights I get while reading.