We all know that world-class writers write differently from the rest of us. What I didn’t know — at least until recently — was how differently some of them read.

Check out these links to the private books of two pretty fair writers: Mark Twain and David Foster Wallace. They’re worth exploring, because 1) it’s as thrillingly close as you’ll get to the engine room of their minds; and 2) because they provide a vivid (and for me, utterly humbling) lesson on how to truly read.

For most of us, reading is a “lean-back” experience; a warm bath. Not these guys. They’re on the balls of their feet, swords drawn. DFW and Twain  challenge, criticize, scribble new ideas, tease, steal, improve, admire. They fully engage with the work. It’s like a writer’s version of a vigorous athletic workout.  Because, I’d like to suggest, that’s precisely what it is: an intense firing of their circuitry; deep practice in excelsis.

On the surface, this seems like a small shift — after all, scribbling a quick note versus thinking a thought. But the act of writing is profoundly different than thinking because it forces precision and it creates a record that can be linked to other scribbles. These notes are a kind of playing field where thought happens; without the marks on the page, the thoughts float up and disappear.

In most circles, particularly schools, marking up books is discouraged, even forbidden. But should it be? With the possibilities of e-books, could this sort of sharp-pencil dueling be encouraged, even taught?