The best horror writer of all time is H.P. Lovecraft.
Lovecraft is scary. Lovecraft’s little finger is ten times more scary than all of Stephen King’s novels put together. The only horror writer that can even come close to Lovecraft’s scaritude (I made this word up) is Edgar Allan Poe, but even then, comparing Lovecraft vs. Poe is like comparing Yog-sothoth to, uh, say, Cthulhu himself. Now I am sounding like a horror nut.
I love to read Lovecraft late in the night. That shit is more creepy than the lame and repetitive creepypastas you get from /x/ or creepypasta.com (by the way, the new Jadusable/Majora’s Mask creepypasta is really good. Look it up).
I strongly recommend that you read up some Lovecraft. You could never find finer horror elsewhere. Lovecraft is truly the master of the craft.
You can download and read Lovecraft’s finest short story, THE CALL OF CTHULHU (in PDF).
You can download Lovecraft’s collected works (133 stories) plus the fake Necronomicon here.
I think the downloads are all legal since the copyright period for Lovecraft’s works has ended. As if this has ever stopped you before. 😉