Not a horror film?

It's certainly scary/creepy but if you expect something like The Exorcist or The Omen you might be a little disappointed. It's a study of what happens to the mind when emotions are buried and not dealt with. Is the Babadook representative of an emotional monster or is he real? The short answer is he's both. Psychological problems are very real but how they manifest is another thing and can be as dangerous as any real physical entity. So did the mother create the Babdook book? No one's telling but one would think yes, she did (she used to be a writer and she made the offhand comment that she did some kid's stuff). Plus the mom never says to her son that she loves him, even though he says it several times to her. The inability to love your own child is a breeding ground for all sorts of psychological instabilities, especially when you're all alone, lost your beloved husband, sleep deprived, overworked and dealing with a precocious, overly aware seven year old child. And the ending? Is it telling us that problems don't just miraculously go away, they are always there under the surface and need to be dealt with, worked on, coddled and pacified. Mental illness is like that.