I'm working my way through Drawing on the Right Side of the Brain by Betty Edwards, and one of the early exercises is to copy an upside-down line drawing. Right-side up, this is what I got:
There's a few lines out of place or missing, and the hands went badly for me, possibly because I was thinking of them as hands and not just lines. But I'm pleasantly shocked at how well this came out and I'm ploughing through the rest of the book. It's rather word-heavy, especially for a book saying that the problem is the left side word-centric brain is the part that can't draw, but there's useful information there.
I'm also looking at The Natural Way To Draw by Kimon Nicolaides as a possible follow-on book.