I was recently introduced to the word “marginalia.” It’s a word that refers to notes and marks made in the margin of books. Lots of people do this, while others view their books as treasured possessions never to be marred.
The first pieces of marginalia were actually in Bibles. Many older Bibles contained illustrations as well as notes for liturgical purposes.
My grandfather used to scribble in his books, often noting what he did the day he read that page. Odd notes about what his kids were doing, even patterns for wood carvings traced on a page. Not sure that’s how it should be done. . .
If you’d like to know how to start doing Marginalia, consult Mortimer J. Adler’s article “How to Mark a Book.” Or this article about applying Adler’s advice, “Reading Actively.” Or perhaps read “A Weapon for Readers.”