Edwards: Drawing on the Right Side of the Brain
A classic literature for every artist. "Drawing on the Right Side of the Brain" is a common term for every professional creative. Luckily you can find this book in almost every second-hand book store. Bookmans has at least 7 or more copies of this book in their store.
When you're interested in drawing, to learn more about the history of drawing, expressions and improve your skills with exercises I do recommend to read this book! It's revealing and helpful.