In his Essay on Diseases Incident to Literary and Sedentary Persons (1769), Samuel Tissot warned that ‘the devourers of books, who exhaust themselves only by reading, should desist as soon as they find their comprehension more than commonly slow, their sight moaty and dimmish, or their eyes hot and watery.’ Undeterred, I stayed in bed last Christmas Day until 4 p.m., reading Lost Illusions.