>Reading a book should be a conversation between you and the author. Presumably he knows more about the subject than you do; if not, you probably should not be bothering with his book. **But understanding is a two-way operation;** the learner has to question himself and question the teacher, once he understands what the teacher is saying.
>**Marking a book is literally an expression of your differences or your agreements with the author.** It is the highest respect you can pay him.
— Mortimer Adler, *[How to Read a Book](https://www.amazon.com/dp/0671212095/ref=as_li_ss_til?tag=braipick-20&camp=0&creative=0&linkCode=as4&creativeASIN=0671212095&adid=1X3HJZ3VZXVA9Q5DEQCE&)*. via [Brainpicker](http://www.brainpickings.org/index.php/2011/12/14/how-to-read-a-book-marginalia/)
Caterina Fake’s [copy of Ulysses]((https://secure.flickr.com/photos/hinkeb/5232293964/)), which inspired the founding of the reading & annotation community [Readmill](http://readmill.com/) by Henrik Berggren. [CC BY NC SA 2.0](http://creativecommons.org/licenses/by-nc-sa/2.0/)
Marginalia in *[Merckwürdige Nachricht aus Ost-Indien, Reise- und Missionsbericht](https://de.wikisource.org/wiki/Merckw%C3%BCrdige_Nachricht_aus_Ost-Indien)* by Heinrich Milde (1676-1739). Public domain via [Wikimedia Commons](https://de.wikipedia.org/w/index.php?title=Datei:Merckw%C3%BCrdige_Nachricht_aus_Ost-Indien_10.jpg&filetimestamp=20061212105534).
*Julius Caesar* marked up by students and teachers [using co-ment](http://www.co-ment.com/category/usecases/).