1) I limited myself to the second half of the century, as I don't think I'm sufficiently familiar with the years 1900-1949.
2) There are three short story collections, because those collections and those authors (both of whom produced far more short fiction than novels) had to be on this list. In the case of Klein, I simply feel that "The Events at Poroth Farm" is a far better work than The Ceremonies, his massive – I would say bloated – expansion of the novella.
3) No one author was allowed to appear more than once.
4) The absence of a few others bothers me. Thomas Harris, for example.
5) The list is unranked.
6) Yes, 2000 was the final year of the 20th Century, not the first year of the 21st Century.
1950-2000, Twenty Best Horror Novels (Plus Three Short-Fiction Collections):
1. Mark Z. Danielewski, House of Leaves
2. Stephen King, Pet Sematary
3. Shirley Jackson, The Haunting of Hill House
4. Thomas Tryon, Harvest Home
5. Clive Barker, The Damnation Game
6. Peter Straub, Ghost Story
7. Ira Levin, Rosemary's Baby
8. Toni Morrison, Beloved
9. Ramsey Campbell, Ancient Images
10. Robert Bloch, Psycho
11. Ray Bradbury, Something Wicked This Way Comes
12. John Gardner, Grendel
13. Anne Rice, Interview with the Vampire
14. Angela Carter, The Bloody Chamber and Other Stories
15. T. E. D. Klein, Dark Gods
16. Kathe Koja, Skin
17. Richard Matheson, I Am Legend
18. Katherine Dunn, Geek Love
19. Patrick McCabe, The Butcher Boy
20. Iain Banks, The Wasp Factory
21. Harlan Ellison, Deathbird Stories
22. Anne River Siddons, The House Next Door
23. William Peter Blatty, The Exorcist