I believe the term irony applies extremely well in this situation. Stockett has written a book about a book that through word-of-mouth becomes a popular bestseller, and that book she wrote? It's a popular bestseller. I wonder if she wondered about that. Every author hopes it will happen.
There's a good reason it's popular. It's extraordinarily well-written, in different voices no less, includes several mysteries that leave you on the edge of your seat for pages and pages, and... dare I say it... assuages our white people's guilt. I'm speaking only for myself here, but the righteous indignation that I felt when reading about the treatment of black women in the South in the 60s comes from the fact that I am both removed from it (by the passage of time and lots and lots of legislation) and still in it (why else the need for diversity training?). I firmly believe we need a lot more books like this, if only to surface these feelings on a regular basis.
There's no happy ending to this novel. There are some satisfactory conclusions, but Stockett makes sure we don't forget the overall environment of time and location, and that there are myriad small and large changes still to take place. If I have any quibbles with the book, it's that the satisfactory conclusions are a bit obvious, and in at least one part, forced. Because the rest of the story is so believable, this barely registered with me until I had to think about writing a review.