The Leader's Handbook takes years and years of research, and new management ideas, and ties them all together, beautifully. Deming was right, but it was often difficult to translate his work out of manufacturing, or to point to the scientific support for his ideas.
Peter Scholtes has put together a more approachable take on Systems Thinking, based on the work of the great Japanese and American systems thinkers, and backed by the work of Alfie Kohn, and Action Science researchers.
That he manages to do this in a holistic way, without obvious seems or disconnects, speaks both to his understanding of the subject, and the cohesiveness of our growing understanding of how the human mind and social interactions work.
If you're looking for an eminently practical, completely doable, and very readable book on systems thinking, transformation, and change, start here. Read the rest if this gets you interested, but by itself, it should be enough to change your thinking, and your approach, to everything.