On Photography was published in 1977 and has not been out of print since. That fact alone suggests Sontag was doing something more than journalism. She was building a framework, and frameworks built well outlast the specific occasions that prompted them. Fifty years on, the book reads as both essential and incomplete — which is a more interesting verdict than either pure endorsement or dismissal. What Sontag got right was the fundamental argument about photography’s relationship to reality.