So... there's insight.
And then there's metaphysics.
The insight, the essence of nonduality is simply this: rather than there being a zillion fragmentary first causes, Reality is a singular (or non-numerical) happening.
That’s the crucial timeless revelation.
The metaphysics on the other hand is the attempt to determine the nature of this Reality.
Engaging perhaps, but ultimately a futile pursuit - how to contain, decode or formulate this ineffable Source?
Metaphysics and philosophy fill the books and websites, blogs and forums. They give rise to academies and conferences... gurus and experts.
Meanwhile... the insight is simple, direct and visceral.
Go for a walk in the woods and sit by a river. It will soon become clear that there is not you and Life... Life is all there is.