Wow, it’s hard to believe this is the first novel written by Jane Smiley, the author of “A Thousand Acres,” “Moo,” and The Last Hundred Years Trilogy. It is excellent, especially if you are an aficionado of horses—equestrian competitions, dressage, and all that. The plot is engrossing, the characters are intriguing, and I pretty much read it straight through. Kate Karlson, the matriarch of the book, is a difficult, obsessive person, whose relationships with her husband, teenage children, and horses make for a compelling story. The title refers to the condition of single-minded focus, at the cost of everything else. Too true.