Worth quoting the preface in full, as it elegantly gives you a feeling for the rest of this often quoted book:
Illness is the night-side of life, a more onerous citizenship. Everyone who is born holds dual citizenship, in the kingdom of the well and the kingdom of the sick. Although we all prefer to use only the good passport, sooner or later each of us is obliged, at least for a spell, to identify ourselves as citizens of that other place.
I want to describe, not what it is really like to emigrate to the kingdom of the ill and live there, but the punitive or sentimental fantasies concocted about the situation:not real geography, but stereotypes of national character. My subject is not physical illness itself but the uses of illness itself as a figure or metaphor. My point is that illness is not a metaphor, and that the most truthful way of regarding illness – and the healthiest way of being ill – is one most purified of, most resistant to, metaphoric thinking. Yet it is hardly possible to take up one’s residence in the kingdom of the ill unprejudiced by the lurid metaphors with which it has been landscaped. It is toward an elucidation of those metaphors, and a liberation from them, that I dedicate this inquiry.