I've just read this, has anyone else? I've read most of her historical novels and was finding them a bit same old, same old. I was very pleasantly surprised that she could write something so different. I found it a really unsettling book and didn't know whether to jump for joy at the ending or get really depressed.
I've read it - grabbed it from the shelf in the library in desperation one day and read it on a train journey. I thought it was awful, I'm afraid. The way that the mil was presented as a sort of cheesy cartoon Mrs Danvers figure was just silly and the ending was, quite frankly, ridiculous.
I stopped reading her historical ones, for the very reason you've said, but they are works of genius compared to this one imho.