As You Are - Rosedale Mansion Series, #1

A playboy with an agenda, a historian with trust issues, and a mansion with deadly secrets. It's the summer of 1994 but to Monica Bishop it is more like 1894. Ever since she was a child, Monica has felt a connection with the ghosts at Rosedale Mansion, thinking of them as family. And she has a plan to make them much closer. Graham Rosedale has spent his life trying to escape his family, but a bargain with his father has him spending the summer at a literal museum dedicated to them.
Graham does not believe in the supernatural, but he feels spellbound by Monica. He knows he should stay away; he has a job to do and no interest in complicating his life, but Monica is strange and tempting and will make him reconsider everything he believes. His time at the mansion is limited. Her attempts at pulling back the veil to the world of the dead might mean they are both short on time.