Interesting article I really liked the last part, surprising!
I'm not a fan of people writing in the library books because I find it distracting, especially if the words are underlined. If a textbook is just a bit underlined I don't mind it but I've had to work with textbooks where you could barely see the writing anymore because of how heavily underlined it was, so I'm partial to textbooks too.
I like the library books because they have that "used" look but I do prefer no one writes in them or if they do, just keep it to a minimum.