What is Advaita Vedanta? – Experience and Knowledge by James Swartz is a short but well written and compact guide to Advaita Vedanta and non-duality from 2003. From the book:
“The Upanishads, the source of Vedanta, say that before this creation was, the self, limitless being, was. It further says that this self continues to exist outside of time and is therefore eternal. And it states that no action one can perform will ‘gain’3 this self, even though it is an ever-present reality… because actions are limited while the self is unlimited. Therefore it is at odds with Yoga on this issue. The discovery that one is the limitless self is presented as liberation or enlightenment by Vedanta.”
Language title : What is Advaita Vedanta? Experience and Knowledge