A Course in Miracles is the source text of many spiritual teachers and I highly recommend that you buy it. Its a book that you can open at any page to offer you great wisdom.
A Course in Miracles: Combined Volume >  

However it's not an easy book to read! I recommend you also buy A Return to Love: Reflections on the Principles of "A Course in Miracles" by Marianne Williamson.

Marianne was the spiritual advisor to Bill Clinton. You might have come across this famous quote written by her. (It was wrongly attributed as spoken by Nelson Mandela at his inauguration):-

“Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure. It is our light, not our darkness that most frightens us. We ask ourselves, Who am I to be brilliant, gorgeous, talented, fabulous? Actually, who are you not to be? You are a child of God. Your playing small does not serve the world. There is nothing enlightened about shrinking so that other people won't feel insecure around you. We are all meant to shine, as children do. We were born to make manifest the glory of God that is within us. It's not just in some of us; it's in everyone. And as we let our own light shine, we unconsciously give other people permission to do the same. As we are liberated from our own fear, our presence automatically liberates others.”

The Disappearance of the Universe: Straight Talk About Illusions, Past Lives, Religion, Sex, Politics, and the Miracles of Forgiveness by Gary Renard.
This is a great book with an intriguing story that you don't have to believe to enjoy its message. Its 'A Course in Miracles' message told via an amusing story.

The Translucent Revolution: How People Just Like You Are Waking Up and Changing the World by Arjuna Ardagh.
Millions of people from all walks of life are experiencing a deep change in awareness, an experience marked by a new sense of well-being, and increasing joy in life, a diminishing of fear - including fear of death - and a natural impulse to serve the world in a real way. This book describes this awakening and is a great introduction to 'Deeksha'.