Some of my favorites for professional development are:
Crucibles of Leadership by Robert J. Thomas. How intense and challenging experiences can be some of the the greatest source of leadership learning. Includes tips on HOW to learn from those kinds of experiences.
The Courageous Follower, by Ira Chaleff. Wonderful book about the dynamics between leaders and followers--and the responsibility that we have as followers to stand up to and for our leaders.
Building the Bridge as You Walk on It, by Robert Quinn. Kind of a variant on servant leadership. A great read, full of wisdom.
The Set-Up-to-Fail Syndrome, by Jean-François Manzoni and Jean-Louis Barsoux. Talks about the toxic impact of low expectations and how they send performance into a downward spiral. Has lots of important insights for public managers.
Many Unhappy Returns, by former IRS Commissioner Charles Rossotti. An epic tale of organizational transformation.
Endurance: Shackleton's Incredible Voyage, by Alfred Lansing. One of the greatest stories of crisis leadership ever. Simply incredible.
You can see more of my favorites (including many that are specifically about leadership in government) in the book section of at GovLeaders.org