Most of us have, at one time, been obsessed with something, but how did obsession become a mental illness? This book examines literary, medical, and philosophical texts to argue that what we call obsession became a disease in the Romantic era and reflects the eras anxieties. Using a number of literary texts, some well-known (like Mary Shelleys 1818 Frankenstein and Edgar Allan Poes 1843 The Tell Tale Heart) and some not (like Charlotte Dacres 1811 The Passions and Charles Brockden Browns 1787 Edgar Huntly), the book looks at vigilia, an overly intense curiosity, intellectual monomania, an obsession with study, nymphomania and erotomania, gendered forms of desire, revolutiana, an obsession with sublime violence and military service, and ideality, an obsession with an idea. The coda argues that traces of these Romantic constructs can be seen in popular accounts of obsession today.