Book excerpt: The case study of John has provided a unique insight into the nature of visual agnosia and more broadly into the underlying processes which support human vision. After suffering a stroke, John had problems in recognizing common objects, faces, seeing colours, reading and finding his way around his environment. A Reader in Visual Agnosia brings together the primary scientific papers describing the detailed investigations for each visual problem which the authors carried out with John, known as patient HJA. This work was summarised initially in To See But Not To See (1987), and 26 years later in A Case Study in Visual Agnosia Revisited (2013). The chapters are divided into 6 parts corresponding to the key areas of investigation: Integrative visual agnosia Perception of global form Face perception Colour perception Word recognition Changes over time Each part contains a short introduction, written by the two leading researchers who worked with John, which highlights the relations between the papers and demonstrates the pathway of the case analysis. The book will be invaluable to students and researchers in visual cognition, cognitive neuropsychology and vision neuroscience.