Could have been a cult classic, just classic.

Rating: 6/10 (15 December 2017)

I will use the succinct last paragraph of another reviewer who summed it up perfectly:
But still, there is one thing I felt was handled wrongly. Throughout most of the film, there are hints thrown, abundantly, that the Babadook isn't real. The phantom cockroach infestation, when the neighbour's name is Roach. Or the casual mention that Amelia used to write, "kids' stuff", which is a huge wink that she is the one who wrote Babadook, and probably then stitched it together after tearing it up. This all ends up being a distraction, smoke and mirrors, when we are clearly told the monster is real. And it feels rather cheap. Personally, I feel that the story should have followed that narrative and simply deliver a mother who hallucinates, goes insane and murders her son. It wouldn't be a twist or anything, it's been done. A lot. But the end result would be much scarier. Though perhaps too morose and likely not crowd-friendly, but ending up with some sort of cellar-bound incarnate horror pet felt out of character.