All writing, at some level, grows out of obsession—the need to get our most intense and unwieldy feelings down on paper so that we might begin to see them clearly, or persuade others that our passions matter. But sometimes the obsession is right on the surface of the plot— is the plot. An obsession makes a strong engine for a novel, engendering intense prose and risky choices. All of the books on this list were on my desk and in my mind when I wrote Mare , a novel based on my own experience—and my own obsession. In Mare , the protagonist takes on the casual, part-time care of a horse, in part to avoid thinking about a future in which she will not have children. When her feelings about the horse turn into affection, and, later, obsession, she struggles to explain their strength to herself or others. After all, as another character insists—the mare is “just a horse.” Sure, in pony books girls are obsessed with horses.…