The Demon Duke by Margaret Locke
This is a sweet, romantic story that deals with how people with unexplained medical issues were treated. Damon is such a captivating and charming man. He's kind and caring and hurt and vulnerable. Grace is a quiet, plain speaking woman who would rather live in a library than deal with the ton. There is an instant connection between them as soon as they meet. He tries outrunning his feelings, because he thinks he's a monster. But Grace doesn't see a monster, she sees a lonely and hurt man. There are some very fascinating characters, and a few real dirtbags. This is so engrossing and romantic it makes your heart melt.