The Invisible Kingdom opens with the statement that this is not a typical story about illness because it lacks a clear beginning. O’Rourke proceeds to describe her own experience with illness as one that has no obvious narrative blueprint, and instead offers a variety of ways that her illness might be narrated. Significant moments within the circular narrative style include finding a mysterious rash on her arm along with other unexplained symptoms. In the face of the unknown, O’Rourke turns to research, healers, doctors, books, and others’ experiences to understand the reasons for her suffering, and her ultimate desire is for recognition of her experience as valid. O’Rourke makes the distinction between living with a disease that is known versus living with an unrecognized autoimmune disease. Since 2012 when O’Rourke first became acutely ill, the discussion of autoimmune diseases has transformed, particularly with the onset of COVID-19, which gave the public a sense of how the same virus can interact with different bodies in completely different ways.

Part of the difficulty for those experiencing unknown diseases is that there is a long, historical link between undiagnosable illness and emotional afflictions.