Recs if you like The Immaculate Void...

Existential Dread Galore. Horror so mind bending that will leave you ponder meaning of all things. Horrors from beyond time, reality & universe.

Books about paranormal/extraterrestrial detective agencies and espionage

Cosmic horror is hard to define, because it takes several forms. Gods, cults, monsters beyond comprehension, madness, etc... and also wildly different forms (one can argue that the Backrooms and Bloodborne inhabit different sides of a spectrum). I'm setting out to read more, and this is what I have read and still have to read. If a book doesn't qualify, I'll remove it after finishing it.