This little known 1901 novel by Joseph Conrad and Ford Mattox Ford (ne Hueber) is a precursor to such works as William Golding's much later novel of the same name; the hugely (and in my opinion, undeservedly) popular "Matrix" movie series; and also to another (originally) dark-horse story, "THEY Live". The ahead-of-its-time idea of these tales is of a type of being - whether a new species of hominid, digitally generated superhumans, or, as here, an extra-dimensional creature - which outwardly resembles man and woman, but which, mainly by virtue of having high intelligence unburdened by emotion, slowly takes over the Earth from its more sentimental predecessors.
The idea of this, so to speak "anti-Vulcan" type being able to infiltrate, dominate, and at last annihilate, all proximate competition resonates deeply with us because, really, it is more than an idea: it is history. Or, more precisely, prehistory: The reason we homosapiens believe ourselves to be alone "in God's image" amongst "the beasts that perish", or, in the words of the brilliant ethologist Desmond Morris "a kind of fallen angel rather than a naked ape", is more than probably because, at some point in prehistory, homosapiens *simply and ruthlessly, wiped out every other hominid - and perhaps even every anthropoid - that could reasonably(!) compete with us for the inheritance of the Earth*. Then, with our closest cousins gone for some 10,000 years, we began to believe the flattering myth that there never existed any creature closer to us than the relatively stupid chimpanzee, and the relatively harmless bonobo; that we alone were valued by the Heavens; even, that, like the Inheritors of the Conrad/Ford story, we were descended not from a pitiful lemur-like beast in the primeval forest, but from "a higher dimension", be it Eden, or the apex of Aristotle's "Chain of Being". In the words of another brilliant social commentator, Howard S. Schwartz: "We pushed reality back until it became a rumor, then we denied the rumor".
I highly recommend this deeply insightful, metaphoric novella, by two of the finest writers in English.