Do you want mysterious knowledge? The Cloud of Unknowing is an anonymous work directly from Chrsitian Mysticism. It was written exclusively in middle english, but now you an get it updated in an English that you can understand.
This is a powerful spiritual guide that any practitioner should add to their library. This is Christian meditation at its finest. A guide to contemplative prayer that suggests that the way to know God is to abandon consideration of Gods activities and attributes. Be coureageous enough to give into the realm of unknowing. Then and only then will you be able to glimpse at Gods true nature.