Rather than a book, I would recommend a MOOC course (Coursera, EdX) on business strategy. A book is going either going to be too dry or from a certain perspective that in isolation may not be very helpful.
Strategic Planning and Execution via UVA
Courses 3,4,5 from The University of Illinois Strategic Leadership Management Specialization
For general reading, "Forces for Good" by Crutchfield and McLeod-Grant, "From Good to Great" by Jim Collins (I didn't care for his non profit section, but the general message is strong), and Joan Garry's Guide to Nonprofit Leadership all may be useful to you, but won't be the definitive source for information.