For women writers, motherhood is a tricky subject—well worn yet inexhaustible. For every book that celebrates children as miracles, there is another that describes the guilt of screwing up or getting Botox while pregnant. The subject is a cash crop: universally of interest, unlikely to go out of fashion, potentially controversial, and probably heartwarming. For a poet, the rules are different. The topics—labor, making cookies, postpartum depression—may be the same, but poetry is not naturally instructive. Rebecca Wolff’s poems about motherhood in The King, for instance, are ironic and dark,