The next few pages are all in on a pebble-drawing exercise, to get used to shadow, light, sources, reflections, etc. I still don't get hatching, but I just tried to shade and while it doesn't look a lot like the provided end result, it's not bad. It gets the idea across if nothing else, and I did enjoy the light points, light in shade, shadowline, and other concepts.
Maybe my hand-eye co-ordination just isn't up to snuff, but I don't get how artists can draw the same line over and over, and the same character over and over, and they always look like the character. I draw and my hand/ wrist flicks in different directions no matter how much I try to control it, and it becomes a mess.