How does light transform the objects it shines upon? What are the consequences of such a metamorphosis on architectural thought? This visually arresting book seeks to answer these questions. Book of Hours presents the research of Mexican architect Frida Escobedo (born 1979) on this topic. Escobedo designs and restores housing, community centers, art venues and hotels. In 2018, she became the youngest architect to work on the Serpentine Pavilion, and the second woman to be invited after Zaha Hadid. Throughout her oeuvre, Escobedo has continuously probed the transformative effects of light on matter. This volume compiles stills from time-lapses Escobedo meticulously filmed during her research; these stills illustrate the interplay between light and shadow throughout the day. Its translucent paper mimics the permeable barrier between light sources and objects, underscoring the impermanence of matter.