One line of Alberto Manguel's "Ideal Reader" essay goes: "Writing on the margins is a sign of the ideal reader. "

I read the essay for a literature class in high school. It's a really nice essay--perhaps more of a poem, even--but honestly, it made me feel pretty inadequate. I've always wanted to be the sort of person who writes in the margins and does other things that make me "an ideal reader," but...I never have. And of course that's something silly to feel insecure about, but nevertheless it makes me feel, I don't know, less intellectual? Less like I have a truly deep connection with a book, maybe.

Like a lot of you have said, it's mostly because I don't know what to write. Aside from books where I have to take notes for class or whatever, I don't really think of things that are worth writing down.

So what do you guys write in your books? Your reactions to things, questions you have? And when you underline, why do you do so? Because a line sticks out to you for a particular reason--because the language is striking, because you actually plan on returning to that page and want to find that quote?