I don't read horror novels as a rule. I understand Mercedes Lackey's three Diane Tregarde novels were considered "horror," but I just gulped at a couple of the graphic parts and went on. Otherwise I don't enjoy the "cut-and-slit-and-bleed" school of novel writing. Besides, real life can be much worse:
I just finished reading Stewart O'Nan's The Circus Fire, which is darned enough horrifying for me. It's the true story of July 6, 1944, in Hartford, Connecticut, when the "big top" caught fire at the matinee performance of the Ringling Brothers Barnum and Bailey Circus. The tent was waterproofed with a combination of paraffin and gasoline and became an inferno in minutes. People crowded out the exits, including having to cross cages at two exits blocked by animal ramps. Some people just walked out, frightened but unharmed. But most were caught in a maelstrom of terrified people escaping the pitch-hot flames. Some were heroes, some trampled others in their efforts to get out. Some died there, some were buried under others and survived although badly burned.
O'Nan has taken the text of depositions, talked to survivors, combed the newspapers of the day, and come up with a book so vivid you feel as if you are there. Especially vivid--and horrifying--is the description of the melee in the tent, the smell of burnt flesh, and the descriptions of the dead and wounded. The book also covers the recovery of several badly burned children and the investigation into the cause of the fire, which was never determined.
At all times it was so graphic I had to just put it down for a while several times and go do something else. But it was a good read.