I was really interested in the subject matter of mediumship and felt Alison's ability was treated in an interesting matter of fact way by mantel, which was refreshing. 
There is a lack of description in terms of characters at times which makes it difficult to get to know or care about them. 
The world created by mantel is lifeless and horrible, there doesn't seem to be any relief throughout the book, I don't know how anyone would be able to call it humourous. 
Devoid of plot and intensely dark. 
I kept reading to see how it would end but maybe I shouldn't have bothered.