Yesterday I finished reading Jacques Vallee's book Passport to Magonia. It posits the hypothesis that the modern UFO phenomenon is actually the latest chapter of a millennia-old story and that basically the greys, the fairies, the religious apparitions, etc are all just different disguises of the same mysterious intelligence that has been toying with us since the dawn of time, and whose true motives remain unclear. He thinks that trying to catch UFOs is as pointless as chasing fairies, and that we should instead focus on analysing the influence that these stories have had on our history and culture. In an interview he offered the suggestion that we might be dealing with some kind of mental (metaphysical?) control system, and expressed an interest in devising methods to proactively test it, but I don't know if he ever followed up on that. Anyway, as outlandish as this is, it kind of makes sense to me.
What is so outlandish about it? Clearly there is a conspiracy of massive proportions surrounding this aspect of our humanity. Are we to believe our ancestors to be so genius as to have created the precursors for our modern world and yet have no idea what reality is? There are discrepancies between mainstream history and alternative history.
A book that I love also addresses the metaphysical, Haruki Murakami's 1Q84. It's fiction, but also an extraordinarily entertaining read. Most of Murakami's books and stories touch on the metaphysical, but this one is more clear-cut and accessible than his other novels, I think (although it still has dead ends, including an antithesis to Chekhov's gun). The book is a monster though, so you trade clarity for sheer volume.
A shorter read that also deals with a metaphysical sort of reality or dreamscape by Murakami is Hard Boiled Wonderland and The End of the World. It's two novels in one. All the odd chapters are Hard Boiled Wonderland and the even chapters are The End of the World. I recommend read through all the odd ones first. Then go through and read the even chapters. Hard Boiled Wonder land is a sort of cyberpunk novel and the end of the world is kind of a fantasy story or dream like story that's kind of hard to explain. It is an absolutely fascinating book, and it was my first exposure to Murakami. I've read a couple of more since then (Wind Up Bird Chronicle and After Dark).