Contributors from around the world offer wide-ranging (and sometimes controversial) discussions of the state of research in photocatalysis. Emphasis is on the surface science of catalysis, especially at the gas/solid interface. Eighteen chapters explore topics ranging from the interaction between light and matter, colloidal semiconductors, and the thermodynamics and kinetics of photocatalysis, to photocatalysis in homogeneous and heterogeneous phases, photo-electrocatalysis, and catalysis in energy production and water purification.