The idea of horror has always captured my imagination much more than have actual attempts to use it in art. Most, it seems, appeal to gore, physical pain, weird supernatural stuff–it seems my definition of horror simply differs from that which most use, and others’ approach to it usually repulses me.
Real horror, I think, relates to surprise, and to awe. To the gradual (or sometimes sudden) realization that the world is not what it at first seems, and to the awareness of how little we understand of that world, and of ourselves. The best horror, it seems, is the truest–not about the psychotic killer, the ancient vengeful spirit, or the monster under the bed, but about the monster in your head, in the society around you, or both. The best horror isn’t effective because the author pulls you into a world of fantasy–it’s effective because the author reaches into your world. Because she grants you a glimpse into the terrifying corners of your own psyche, or reveals for a moment the darkness that your community usually manages to ignore.
The two best horror stories I’ve yet read are both fairly short. M. Rickert’s Bread and Bombs is a relatively recent one, and published online with the author’s permission. Shirley Jackson’s story The Lottery was published a few decades ago, and is available in various collections as well as in probably-copyright-violating online copies. Both are well worth reading.