Dark Matter - Michelle PaverAn unsettling tale set in the isolation of an Antartic winter.
Eutopia - David NickleBlimmin creepy, I had trouble sleeping after this one. You can read my review here and an interview with the author here.
Tokyo - Mo HayderActually several of Mo Hayder's books have left me not wanting to turn the light off and she isn't a really a horror writer! I think some of the subject matter in Tokyo (alternative title The Devil of Nanking) is pretty disturbing but I also learned a little bit of history.
World War Z - Max BrooksI don't think it's all that scary but you can't have a Halloween list without zombies and this is one of my faves.
It - Stephen KingGaaaah scary clown! Seriously, were clowns even scary before Stephen King came along? I'm not that sure. Though pretty much any Stephen King will set you up for this Halloween.
Undead and Unwed - MaryJanice DavidsonHalloween has it's fun side too and even if the series goes downhill, the first Queen Betsy book is a hilarious take on the vampire sub-genre.
The Graveyard Book - Neil GaimanA boy who lives in a graveyard and has ghosts for friends. I find Neil's children's books charming without being patronising and this has the perfect tone for Halloween if you don't want a heavy going read.
Dracula - Bram StokerClassic horror. It might not seem all that scary to modern readers, but imagine you were living in 1897 when it was released. I bet it was pretty shocking to its contemporary audience.
The Gashlycrumb Tinies - Edward GoreyThis is actually an illustrated poem but I love it's macabre ABC of children who fall foul to horrible deaths!
The Poems of Edgar Allen PoeTurn down the lights and read aloud...