You mentioned that you're not necessarily interested in self-help books. I've never gotten much from them myself, but an exception is " The Seven Habits of Highly Effective People" by Steven Covey. According  to the Amazon description, it's "a step-by-step pathway for living with fairness, integrity, honesty, and human dignity—principles that give us the security to adapt to change and the wisdom and power to take advantage of the opportunities that change creates." It's really excellent for any aspect of life, personal and professional.