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 era anxieties. Using a number of literary texts, some well-known (like Mary Shelley 1818 Frankenstein and Edgar Allan Poe 1843 “The Tell Tale Heart�) and some not (like Charlotte Dacre 1811 The Passions  and Charles Brockden Brown 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.