Here is a living list of books I recommend. I will be adding to it as I come across books that touch me in some way. Feel free to help me enhance it by making your own recommendations in the comment section.
Tao te Ching- translated by Stephen Mitchell
The Bhagavad Gita
The Yoga Sutras of Patanjali
Buddha- by Karen Armstrong
Siddhartha- by Hermann Hesse
Nature, Man and Woman- Alan Watts
When Things Fall Apart- Pema Chödrön
Be Here Now-Ram Dass
A Path With Heart-Jack Kornfeild
Cutting Through Spiritual Materialism- Chogyam Trungpa