(Note: although the book is over 40 years old, there are spoilers here)
I have no idea whether Ira Levin considered himself a feminist, but his two most famous books - Rosemary's Baby and The Stepford Wives - took women's often subconscious fears and turned them into full-blown horror. Rosemary's Baby in particular deals with maternal ambivalence and cranks it up to a level of pure terror.
Rosemary's Baby is about a lot of things - pregnancy fears, Death-Of-God theology, the occult, and... Real estate. The whole plot is put in motion because Guy and Rosemary Woodhouse want to move into a nice apartment.The Bramford is a Gothic Revival apartment block modelled on the Dakota (later famous as John Lennon's final residence), and the Woodhouses can't believe their luck in getting a place. Guy is an up-and-coming actor (Levin was also a playwright, and actors don't come off too well here) and Rosemary his bored homemaker wife.
The Woodhouses soon find themselves welcomed by their amiable-but-nosey neighbors, Roman and Minnie Castavet. Rosemary soon tires of them, but Guy, surprisingly, ends up spending more time with the older couple. When Rosemary gets pregnant (under very creepy circumstances that resemble a marital rape), the Castavets show even more interest in her well-being, giving her odd, disgusting health food shakes and an amulet that smells terrible. And yet despite what they say she feels like this is not good for her unborn baby. She becomes increasingly isolated from her younger friends, who remark that she looks wan and dangerously thin (her grandfatherly doctor assures her that while losing weight while pregnant is unusual, it's nothing to worry about).
What makes Rosemary's Baby work so well is what makes all horror stories work: it's utterly plausible until the big occult reveal, and by then it's too late. Like The Shining, the novel works by suggesting that regardless of whether the plot is real or Rosemary is just going mad, it doesn't matter because both possibilities are equally terrifying. (The Exorcist is much less psychologically satisfying, dealing mostly with men's fear of female sexuality but in a rather crude way)
I hope this doesn't suggest that Rosemary's Baby is a heavy book, because it's true to the pulpy nature of the best horror novels. You could read it in a night. And it's also rather funny. Levin makes hay of the fact that the Castavets and their friends are all Republicans who back William F. Buckley for mayor. As well, in Rosemary's drug-induced dream, at one point she thinks she's being impregnated by the late JFK (The book's inclusion on an episode of Mad Men makes perfect sense, because both share a slavish attention to detail; the only difference is that while Mad Men is a period piece, Levin's approach is almost documentary-like) The Castavets are not just evil; they're vulgar and embarrassing, the neighbors from Hell in more ways than one. (One sour note is Levin's stereotypical portrayal of a Japanese man)
Needless to say, Rosemary's Baby is probably the worst thing a pregnant woman could read (among movies, only Alien or The Fly are worse). But it's a (sorry) devilish satire on the whole culture surrounding modern motherhood. I would love a second opinion on whether it's feminist or not. But it made this man realize how weird the whole process is, and nobody can read the book without sympathy for Rosemary.
(Note: it is almost impossible to discuss Rosemary's Baby without discussing the movie and its notorious director, Roman Polanski. I can understand boycotting Polanski on principle, so suffice it to say that the movie is incredibly faithful to the book, and Mia Farrow gives the performance of her career).