There exists a long, passionate, and somewhat batty tradition of writerly appreciation for feline ways, its entries cropping up among the serious work of many otherwise serious people. In The Informed Air (New Directions, 2014), a new collection of Muriel Spark’s criticism and occasional prose, Spark joins the chorus with a paean to her own cat, Bluebell. Spark is known for her novels, not her nonfiction. Yet in this volume’s frequently short and sometimes oddball selections, drawn from the full arc of her career, Spark’s precision and wit are much on display. “Ailourophilia,” too, is funny—but not only that. The