A Certain Slant of Light and Under the Light by Laura Whitcomb

Whether or not they contain ghosts, many books have been described as haunting. Laura Whitcomb's writing is definitely that, especially in her imaginative take on ghosts, A Certain Slant of Light and the follow-up novel, Under the Light.

For more than a hundred years, Helen has been a ghost with no way to communicate with the living. She can see people, but they can't see her -- until one day when someone looks right at her. James is a teenager, alive and well, and he wants to get to know her. The more they talk, the more is revealed about Helen's past, as she struggles to remember her life. How did she die? Why can James see her? Light reveals shades of darkness and traces of hope as Helen struggles to recall her life -- and James begins to make her a part of his life.

I strongly recommend reading A Certain Slant of Light first. Though I suppose you could read Under the Light on its own, trust me, if you know the characters went through in the first book, it will make the second book all the more poignant.

Trivia time: The title of the novel comes from an Emily Dickinson poem.