The Madness of Lord Ian Mackenzie -  Jennifer Ashley
Ian is a very unique hero. He was born in a time when a person with a mental disorder or social issue was put in an asylum. No one understood what was "wrong" with them so they removed them from the population. For some, this was probably not a bad idea. Without the medications and therapy we have today, some illnesses would indeed make a person dangerous. In the case of Ian, he would have been okay with a few understanding people to help guide him. I do not remember the book specifically pointing out what was up with Ian. The characters would not have known so the reader wouldn't know. Can Ian live a normal life? Is it possible for him to fall in love or will he always be alone?

Well this is romance so duh, he finds a super understanding woman who thinks he is swell. Beth doesn't meet the standards set forth by society for women of her era. She is used to being different. Ian is a kindred spirit to Beth. Together they might be the most adorable couple you ever root for.