Year of the Flood by Margaret Atwood. I discovered quite by accident that there is a sequel to Oryx and Crake, that that unsettling ending isn't the end of the story after all.
As with Stephen King (sorry, Margaret, for comparing you to such a mainstream author), I have discovered Atwood's formula. But instead of making me lose interest, this discovery has made me see science fiction wherever I look.
While King creates horror by first making the reader completely recognize the characters and setting (thus bringing the unspeakable horror "home," so to speak), Atwood takes objectionable recognizable things from around us and imagines the worst possible outcome-- X, whatever it is, to the nth degree.
In A Handmaid's Tale, for example, she takes government control of women's reproductive systems and says "what if this got much, much worse?" In Oryx and Crake, she takes commercialism and anti-intellectualism and says the same thing.
Reading her work, you suddenly recognize, in case you missed it, that you are actually living in a dystopia. It's right here all around us, fueled by mass media and the information age, and it isn't destined to get any better any time soon. That's Atwood's formula for horror.
I once heard a science fiction author speak and she said "Science fiction is inventing the future." The dystopic subgenre of science fiction, playmate of horror, operates as a warning--- but does anyone listen? Do we have to invent such an ugly future?