Rosemary's Baby by Ira LevinRead about the other titles on the list.
Widely considered a classic not only of horror but of literature in general, Ira Levin's 1968 novel is less about secret satanic cults and conspiracy as it is about free will and religious guilt. It's even less about the titular demonic tyke than it is the woman who co-spawned it. I talk at length about the author's thematic intentions behind the horror in my Book Vs. Film column from a few months back, but as space is limited here, I will say that Rosemary's Baby is all about mankind's psychological need for organized spirituality, and the lengths a person will go to in order to fill this need. But it's also about the trappings of a patriarchal society, the plight of women in said society, the falsity of a "biological clock," the vanity of status, and the slippery nature of morality—all of it vetted through the sweet-natured, sometimes naive but no less willful and astute mind of our protagonist. If you've only ever seen the Roman Polanski film, you don't really know Rosemary.
Rosemary's Baby is among Kat Rosenfield's top seven scary autumnal stories.