I think Humble Inquiry is a great book to get your mind focused on asking great questions.
https://www.amazon.com/Humble Inquiry
I'm a bit biased on the next two books because I wrote them.
The Consultant's Code, this covers the four pillars all great consultants have.
https://www.amazon.com/The Consultant's Code
The Trust Paradigm, this book discusses how to develop trust with your client. Trust in consulting is based on three directions, your client trusting you, you trusting your client and you trusting yourself. It goes into detail on how to recognize and develop trust principles.