A major problem that I've had with Rowling's prose is that she takes too long to get into the "hearts" of the characters, if she ever truly does in many cases. The characters in The Casual Vacancy are almost uniformly venial and there is little that differentiates them in terms of how Rowling depicts them. Couple that with a 250-300 page length story stretched over 500 pages and a tepid book is the result.