And mostly it changes toward the more complex, more elusive, more difficult to understand.
From this statement I believe your question is about the Ultimate Reality. If it is so, it will always be like this (as mentioned above). The main fault regarding your search is that you are trying to catch it with the organs that becomes formless or unreal (as per your above statement) after a certain period. If so how could you understand it? You should seek it within yourself.
Question: Does the phenomenon itself tell us something about Reality?
Of course, it (the present experience you mentioned i.e., the complexity, elusiveness, difficulty to understand etc.,) shows that our sense organs can never catch it. Since it cannot be controlled by mind or sense organs, understanding of the Ultimate Reality must be something more than understanding or experiencing. That is why it 'seems' to be complex, elusive and difficult to understand.
Is there any literature that explores this?
Advaita vedanta has already named that ultimate reality 'Brahman'. And this word is usually used synonymous to God. If[He who realizes the Ultimate Reality won't see a second thing; even an external God] If we say 'Nothingness'Reality is reality'Nothingness (or Nothingness is reality)', it certainly implies that it is no use seeking it. Advaita vedanta doesn't take you to that idearoute. If itNothingness were so, the UpanishadsUltimate Reality, Kathopanishad wouldn't have announcedexhorted to awake to reach the goal.
https://en.wikipedia.org/wiki/Brahman
https://www.speakingtree.in/blog/brahman-is-the-ultimate-reality