There are so many books about leadership it can be hard to know where to start. Below is a list of recommended reading for new and aspiring leaders.
The 7 Habits of Highly Effective People by Stephen R. Covey. A great introduction to the study of excellence and a practical application of Appreciative Inquiry in a business and organisational context.
Here is a brilliant summary of the essentials of leadership for any leader in any business: Effective Leadership by John Adair