God,
Here are some of the texts that I've read that might be considered quote unquote mystical and might appeal to people craving an understanding of the emptiness of God:
-Manly P. Halls The Secret Teachings of All Ages and The Lost Keys of Freemasonry
-The Cloud Of Unknowing
-The Love of Eternal Wisdom (St. Louis DeMontfort)
-Simone Weil (The Abolition of All Political Parties + Gravity and Grace)
-Kirkegaard, Soren?
-The Blue Cliff Record and The Gateless Gate
Silently Anonymous,
-The Archer