i've done this for years now. it's a great way to maintain attention, single out passages for later read-throughs, and note the weak points of the author for t

i've done this for years now. it's a great way to maintain attention, single out passages for later read-throughs, and note the weak points of the author for the purposes of composing a response or synthesis understanding. one practice that i have used to great effect is circling the names of other authors and other texts which the piece that i'm reading mentions. then, if it's relevant, i can later hunt down the other resources easily. you can do some really cool exploration through certain intellectual movements that you'd never otherwise encounter. using that method i've discovered a few of my favorite authors (edward bernays, walter lippmann, etc). notably, the book that goes into this practice and other scribblings in great detail is the timeless classic, "how to read a book" by adler. there's an entire section describing how to use marginalia to improve your understanding and set the stage for syntopical reading wherein you gain the deepest level of understanding and link-ins with outside information. there's probably enough utility in pencil-reading to give an entire class on it. i can't praise it enough.