In the mid-1970s, Keller started using photography as a medium, in particular Polaroids. In the vibrant New York scene of the 1970s-1980s, he crossed paths with people such as Nan Goldin and Keith Haring, and started to use his art world understanding and contacts to teaching, before becoming, in the 1990s, the Director of the Lausanne art school, ECAL. This book, stemming from a state-funded research project headed by Lionel Bovier, follows this trajectory and gathers together for the first time exhaustive documentation of Keller's work. Including newly commissioned essays by Elisabeth Lebovici, Stéphanie Moisdon, Eric Troncy, and François Rappo, among others, it offers an overview of his professional career.