I feel sorry for J.K. Rowling.
Writing a book is hard. It takes time and effort and a lot of emotional investment. I should think every author worries if anyone will want to read their book, let alone actually like it. Now imagine the pressure of being so famous and so successful. Either people will be desperate to read your book and vocal in their disappointment if it doesn't meet their impossibly high expectations, or they'll be desperate for you to be seen to fail just because you're so famous and so successful.
There is no way Rowling will get an unbiased review. Every reader who has heard of Rowling or of Harry Potter will come to The Casual Vacancy with some sort of agenda. So, yes, I feel sorry for a very successful author.
There's a moral here for us minnows: be careful what you wish for.