Learn more about Sufism online or explore books such as:
Essential Sufism by James Fadiman and Robert Frager (Harper One, 1999)
The Garden of Truth: The Vision and Promise of Sufism, Islam's Mystic Tradition by Seyyed Hossein Nasr (Harper One, 2008)
Sufism: A Beginner's Guide by William C. Chittick (Oneworld Publications, 2007)
Awakening: A Sufi Experience by Pir Vilayat Inayat Kahn (Tarsher, 2000).