I've seen this attitude before - that dark and gritty are synonomous with reality. Bullshit.
Dark and gritty do exist, but to imply that reality is all dark, gritty, selfish, greedy, and evil is just as ridiculous as thinking that reality is all sweetness and light.
People exist in all forms and all flavors. Nobody's perfect, of course, not even my wife, who comes closest, but lack of perfection does not equate to nasty and vicious.
In exploring the dark side of humanity, the question for me, is always, why?
For those who've read the book, what is the answer to that question? Why did JK write this book?*
If I hear a good enough reason I'll take a look, otherwise, meh.
*no, it's not a 'how long is a piece of string' question. this is quite a specific type of story, with specific type of characters, in a specific setting. PS. In anything anyone writes there is a reason, an underlying possibly unconscious reason, but a reason nonetheless. And a novel reflects that. It reflects the author's psyche one way or another - and it reflects an author's integrity, authenticity, sincerity or lack therein. Truth in a novel is not required to obtain commercial success, but it is required for that novel to resonate and gain strong affection from a reader. The 'truth' may apparently simply be 'laughter is good', or 'play is love', or 'lies are damaging' or more complex 'not all good actions produce good results', 'there is no black or white in moral decisions'. (complexity and simplicity are descriptions here only). The only measure of validity, for me, is whether Casual Vacancy resonates a truth or not. In exploring the underclass or hate or cruelty does JK offer a truth? Personally, in my judgement, seeing her in different interviews I'm making a judgement call and say I would imagine no, she doesn't. But if someone tells me they found a truth, that the novel resonated a truth for them, then I'll definitely buy it and read it. Until then, my personal instincts tell me she's playing with a fire she barely understands.