Does the idea of a Science Fiction book filled with Mythos horror sound strange to you? here's my take on it:

HORROR SCIENCE FICTION
By G. W. Thomas

Science Fiction as a genre is many things to many readers. To some it is a literature of ideas, with the intent to explore, to wonder, to question. To others it is a fun-filled adventure category that replaces horses with spaceships and desperados with aliens. Still to others it is an extrapolative extension of the Scientific Method, a way of asking "What if?"

There is another, smaller group (to which I belong) that sees Science Fiction as a vehicle to frighten. Dark SF is a style of writing that has never gained its own moniker (I would never dream of suggesting the unseemly Hor-Sci or Sci-Fright.) This branch of SF takes its power from two connected ideas: SF can explore worlds that are unknown to us. H. P. Lovecraft said fear is the strongest emotion, and fear of the unknown the ultimate fear. Instead of seeing all those new worlds as wondrous and inviting, the SF-Horror writer sees them as terrible, filled with lurking evils waiting to infest humanity.

The scientific horror story begins with H. G. Wells (1866-1946). Precursors to Wells, including the equally famous Jules Verne, tended to see the future or trips to the moon as an exciting moment of exploration, usually led by scientists as visionaries. Wells' brand of SF turns the 'plausible future' into an extrapolation from present facts, as in Wells' "The Land Ironclad" in which he predicted tank warfare 8 years before 1917. Wells was not interested in what did exist but in chasing an idea to its terrible, if impossible, conclusion.

More important than the technological horrors are Wells' monsters. The Morlocks, the Beastmen, the Invisible Man and the Martians are classic SF as well as classic horror. The reader is chilled at the moment when the time traveler realizes the state of things in the future, that Eloi are cattle and the Morlocks their herders, or when the narrator is trapped in the beastmen's hut during the reciting of the litany of the law. "Are we not men?" or when Kemp realizes that the Invisible Man is not simply a victim of an accident but a madman as well, a lunatic armed with invisibility, and finally, this classic scene from The War of the Worlds which is worthy of quoting:

And this was the sum of the Martian organs. Strange as it may seem to a human being, all the complex apparatus of digestion, which makes up the bulk of our bodies, did not exist in the Martians. They were heads--merely heads. Entrails they had none. They did not eat, much less digest. Instead, they took the fresh, living blood of other creatures, and injected it into their own veins. I have myself seen this being done, as I shall mention in its place. But, squeamish as I may seem, I cannot bring myself to describe what I could not endure even to continue watching. Let it suffice to say, blood obtained from a still living animal, in most cases from a human being, was run directly by means of a little pipette into the recipient canal. . . .

Wells turns SF from the Voyages Fantasque of Verne into a varied path, one that can contain all emotions including terror. Dystopic visions of the future like George Orwell's 1984 (1948) or Zamaton's We (1924) owe their freedom to imagine the worst from Wells.

In the early Pulps, monsters were common. Edgar Rice Burroughs and his imitators supplied a steady stream of weird beasts and amazing creatures. The intent was not to frighten the reader but to amaze or excite. It takes a special writer working in the Wellsian tradition to create both fantastic and horrific creatures. Three early writers who excelled at blending horror with a scientific rational were A. Merritt, Clark Ashton Smith and H. P. Lovecraft. All three wrote straight horror and fantasy but in stories like "The People of the Pit" by Merritt and "The City of the Singing Flame" by Smith and "At the Mountains of Madness" by Lovecraft, weird events have a logical basis. It is this quality that makes their fantastic concepts more acceptable to the reader.

The Science Fiction magazines spawned by Hugo Gernsback after 1926 drew SF back towards the Vernian model, but SF would not be limited to gadget fiction. John W. Campbell, the man who innovated SF with the magazine Astounding also wrote one of the masterworks of SF Horror, "Who Goes There?" a tale of a team of scientists in Antarctica who discover an alien that can take its form from others. Campbell's intent was both to frighten but also present his monster as logically as possible.

Since the days of Campbell, SF has been wide open to all types of stories, including the horror SF tale. It is Hollywood that has made things harder for writers. The B-Movies of the 1950s and 1960s filled movie screens with giant locusts, space children and 50-Foot Women. This schlock treatment of horror SF has made it harder to frighten audiences but with films like John Carpenter's The Thing (based on Campbell's "Who Goes There?") and the Alien series the movie industry as undone some of the damage.