Lilith

Original and unabridged text
Lilith is considered among the darkest of George MacDonald's works, and among the most profound. It is a story concerning the nature of life, death, and salvation. In the story, MacDonald mentions a cosmic sleep that heals tortured souls, preceding the salvation of all. MacDonald was a Christian universalist, believing that all will eventually be saved. However, in this story, divine punishment is not taken lightly, and salvation is hard-won.
Mr. Vane owns a library that seems to be haunted by the former librarian, who looks much like a raven from the brief glimpses he catches of the wraith. After finally encountering the supposed ghost, the mysterious Mr. Raven, Vane learns that Raven had known his father; indeed, Vane's father had visited the strange parallel universe from which Raven comes and goes and now resides therein. Vane follows Raven into the world through a mirror.