Well, whatever the traffic will bear. It will sell. And the critics are waiting. I like Harry Potter, but I have no great hopes for her as a mystery author. What gets me is that all these mega sellers in other genres want to try mysteries? Why? Why not stay with what you're good at?
I disliked her writing style in the Potter books so couldn't get into them. I felt she was always faintly patronising towards her audience and her characters. Lord knows what she'll get up to in a mystery novel. Is it for kids, does anyone know? Like an Enid Blyton Famous Five?