I was once sitting in the pastor’s office doing my sermon preparation and one of the members of the church passed by the door and noticed me highlighting my commentary and writing notes in the margins. He stopped and said, “You know, you shouldn’t write in your books. Instead, you should get a separate sheet of paper and write your notes on that. Then you can tuck away your notes inside the book without marring the book itself.” I thanked the person for his kind advice, he walked away, and I kept on highlighting and writing in my book. I didn’t do this out of spite or arrogance, but because I had made a purposeful decision to do so.
Let me frame the matter in a slightly different manner: Would you ever encourage a ditch-digger not to get dirt on his shovel? This was essentially what I thought the kind person was asking me to do—don’t get any intellectual dirt on your nice clean book! For someone who doesn’t do serious study for a living, I can see the point. You don’t want potentially to mar your nice expensive book. But if, on the other hand, you’re trying seriously to study the book, then marking it up is vital to processing the information within.
There have been scads of studies on the history of marginalia—comments written in books. Moreover, there are other studies that I have read that address the superiority of reading paper books vs. e-books. You can’t physically interact with an e-book in the same way you can with a physical copy. When I write and highlight in my books, I’m not just reading—I’m carrying on a conversation, a dialogue, with the author. I highlight important points. I often write descriptive comments in the margin to remind me what the author was discussing, but I also often carry on discussions and ask questions. All this amounts, not merely to reading the material, but thoroughly digesting it.
So, should you mark up your books? In my humble opinion, absolutely! Mark them up! Buy physical copies of books of importance, highlight it, and write in the margins. See how your comprehension compares merely to reading without marking in an e-book. Moreover, if it’s a challenging book, ensure to highlight in one color. When you go back to read the book again at some point in the future (which you should do if you really want to learn the material), highlight in a different color. You might just be surprised at the things that jump off the page. There's one book that I’ve read three times (it was a tough read—Vos’s Pauline Eschatology—he wrote it in Dinglish, i.e., Dutch and English). Anyway, the first time I read it I hardly highlighted anything (I used yellow). The second time I read it about a year later, I highlighted a few more things (I used blue). The third time a read it, I’m not sure what happened, but it was like the scales came off my eyes and I was practically painting each page with the highlighter (I used pink). It seems like virtually every page had pink highlighter on it. I can visually see how I learned more with each reading of the book.
So, don’t be afraid to mark up your books! The ditch-digger doesn’t fear dirt on his shovel, the marksman doesn’t fear gunpowder on his rifle, and the carpenter doesn’t fear sawdust in his shop. The dirt, powder, and dust are signs of someone hard at work. So use your books, mark them up, converse with the author and truly digest what you read.