Yoga-Sutra of Patanjali

A classic work of Indian philosophy that succinctly spells out how the mind works and what is needed to attain liberation
 
Compiled in the second or third century CE, the Yoga-Sutra is a road map of human consciousness—and a particularly helpful guide to the mind states one encounters in meditation, yoga, and other spiritual practices. It expresses the truths of the human condition with great eloquence: how we know what we know, why we suffer, and how we can discover the way out of suffering.
 
Chip Hartranft's fresh translation and extensive, lucid commentary bring the text beautifully to life. He also provides useful auxiliary materials, including an afterword on the legacy of the Yoga-Sutra and its relevance for us today.