This drawing is from the back of sketchbook number eight.
Sharpie® markers are wonderful black markers that will write on just about any surface and they are great for labeling all sorts of things that would be normally hard to write on but they are not conducive to keeping art in archival quality. There is some chemical property that will leach into adjacent paper and leave a ghost impression. Sure, the black is nice and dark and the fat tip of the marker will allow you to cover large areas quickly but be warned, after a few years you will see the leaching occur.
Never ever use them in a sketchbook that contains drawings that you treasure. I used a Sharpie® on the above drawing and the ghostly chemical leaching corrupted five adjacent sketchbook pages in both directions.