The Gift of Therapy by Irvin Yalom
Not every one of the 85 succinct, stand-alone chapters in this book are applicable to coaches, but the ones that are really are a gift.
The Mindful Therapist by Daniel Siegel
Excellent on it's own or as a follow-up to Mindsight. Dense in certain parts - take your time with it.
The Soul's Code by James Hillman
A classic - you've already read it, right?
Presence by Peter Senge et al.
The original subtitle still says it all: An Exploration of Profound Change in People, Organizations and Society.