This is an intense, gritty look at England and Scotland in the 'teens, before and during the Great War. Early on, Donella sets up the distinction between the slow moving, nostalgic image of the English countryside and the dirty, petrol-scented approach of modernity, and the book lives in the latter from then on. This is the searing look at the women's suffrage movement in Britain of 2015's Suffragette, with themes of obsession, mental illness, and what wouldn't yet have been named but looks a lot like Stockholm syndrome. It would be off-putting to say the least if it wasn't the tone you were looking for, if, for example, you just picked it up off a display of fiction about pre-War England, but if you're going for something darker, it's remarkable.
My only reservation is one about structure. Although there is a bit of back and forth in the timeline, it runs linearly for most of the book, meaning that we get the majority of Arabella's story before returning to Donella's. Since the suspense is mostly drawn from Dr. Ferguson Watson's relationship with Arabella, and the impact that it has on his marriage, the most interesting parts are over with before we see their outcome. More frequent alternation between the timelines might have kept the tension a bit higher. That might have made this book a keeper that I'd want to reread some day, but as it is, I still certainly suggest that anybody who remotely thinks it sounds like their thing read it once.