I breezed through "The Miniature Guide to The Art of Asking Essential Questions" by Linda Elder and Richard W. Paul, and I will now recommend this to every manager I know. In fact, if I had to put together a manager's toolkit of recommended readings, this might be included in it.
This guide is an easy read on critical thinking and management. It was a good reminder for me and offered some practical skills and advice. I've become very aware of the discussions I lead and how I can improve upon them through better preparation and facilitation. Asking essential questions is a key factor in successful outcomes.