What is the author's style in Affinity by Sarah Waters?

The language of this novel is modern, but it has a sense of the more formal speech of the time period. While the narrator of this novel is an upper class woman living in 1874, her language tends to be less formal than one might suspect a woman of her class and time period might use. However, the novel is more formal than a typical best seller in modern times, giving the novel an overall sense of the time period and the young woman narrating the story.