'Horrostor' has a great concept: take the Haunted House trope and set it in a modern department store modelled along the lines of Ikea. The cast of characters runs the gamut from earnest store supervisor and sarcastic check out operator to a couple of wannabe Ghost-Hunters. My only reservation is that it feels like a novelisation of the film that seems, on the basis of the novel's original concept, to be almost an inevitability.