The Innovators Dilemma by Clayton M Christensen
Freakonomics - Steve Dubner
Scaling Up, by Verne Harnish
Better Managers = Better Business, by Pete Fullard
McKinsey Quarterly (a wide range of leadership, management and strategic thinking)
Harvard Business Review (a wide range of leadership thinking)
David Clutterbuck (a good resource for coaching and mentoring thinking)
William Buist: Intentional Mastery
Stephen Covey: The 7 Habits of Highly Effective People
R. Michael Anderson: Leadership Mindset 2.0
Nick Howell: Great Coaching Questions
Julie Starr: The Coaching Manual
John Kotter: Leading Change
Caspar Craven: Be More Human
The Five Dysfunctions of a Team: A Leadership Fable by Patrick M. Lencioni