His autobiographical books have been exposed as forgeries by historian
Gitta Sereny. While they contain some true information, they are mostly works of fiction that try to stylize Gray into a heroic figure of historical significance. Sereny, who was an expert on the Treblinka extermination camp, wrote in 1979, that Gray confirmed in an interview to her, that he never was in Treblinka and never escaped from there. Other parts of his autobiographies are fictions, too.