Beloved is the creepiest ghost story I have ever read. Of course this is a ghost story used as metaphor for how haunted these characters are by the past; haunted by their horrible experiences, slavery, violence, humiliation, and guilt. In the central instance the haunting is so powerful that it takes on flesh. Morrison is not the only author to take a trope from genre fiction and use it as a tool to explore a serious theme, but few have done it this effectively.
This is a hard book to give a star rating to because I can't pretend that I enjoyed it. There are scenes in the book so gut-wrenchingly horrible that you have to admire the author's skill in pulling it off, but enjoyment is not a factor. There are sex scenes in this story so awkward and gross that you will not be able to think about sex without experiencing nausea for several days.
I would recommend the work of Octavia Butler to any fan of Toni Morrison. Butler used the tropes of science fiction to explore similar issues of race and exploitation and guilt. Of course Butler's work still gets relegated to genre fiction, while Morrison's is studied in university literature classes. Just another example of how literary critics mistake science fiction for stray dog trying to sneak into their literary yards.