That Hideous Strength,  CS Lewis.  This bloodiest and most disturbing entry in Lewis' Space Trilogy is the only one that stands well outside the series.  Its post-war horror evokes Christian symbolism and the myth of the Arthurian return, but Lewis can't resist some very nasty sterotypes (sadist Nazi lesbians and the angel in the house) amidst his blood and gore.  Perhaps the most pulp of his works as well, when I first read this as a child, I had nightmares for days about the bodyless “head.”