After I bought this book at the bookstore, I read the reviews for it on Amazon. I have to say, the people who are giving this book low marks have seriously missed the point. Which is unfortunate, really, because they're missing out on a lot.
This book differs from a lot of how-to art books in that it doesn't "teach" you to draw. Instead, it coaches you on getting out of your own way, dialing down the inner critic, and pumping up the personal expression with a few drawing prompts at the end of each chapter. Only a few because they don't want to bog you down in a lot of emotionally intense stuff. For example, at the end of the first chapter, you're charged with drawing the human figure. For non-drawers like me, that's a pretty tall order. I can tell you right now, any human figure I draw will be more sticklike than anything from Leonardo da Vinci's notebooks. But perfection or imitation isn't the point of the exercise. Practice (and process) is the point.
Basically, the only way to get good at drawing is to just do it. A lot. But before you can "just do it" you have to give yourself the mental and emotional room to experiment, mess up, and learn without judgement.