Book excerpt: Universally lauded poet Robert Hass offers a stunning, wide-ranging collection of essays on art, imagination, and the natural world—with accompanying photos throughout. What Light Can Do is a magnificent companion piece to the former U.S. Poet Laureate’s Pulitzer Prize and National Book Award-winning poetry collection, Time and Materials, as well as his earlier book of essays, the NBCC Award-winner Twentieth Century Pleasures. Haas brilliantly discourses on many of his favorite topics—on writers ranging from Jack London to Wallace Stevens to Allen Ginsberg to Cormac McCarthy; on California; and on the art of photography in several memorable pieces—in What Light Can Do, a remarkable literary treasure that might best be described as “luminous.”