For a very long time the drawing book "Drawing for the artistically undiscovered" by Quentin Blake and John Cassidy was just catching dust at my book shelf. I didn't have the courage to begin with it, although it's a really funny and special book!
It is "a sketchbook with training wheels". The assignments and the partially filled pages help you to begin, to dare and to learn a lot in the way. And an eraser is not allowed, because the authors don't believe in mistakes! The goal of the book is to give you the ability to sneak into the heart of your subject by going direct. The focus is not so much on the appearance of something, so much as the "something" itself.
Below a few pages to give you an idea:
This is really hard work for me!