What is the setting of Lilith by George MacDonald?

Lilith is set in two parallel universes that coincide in time and space. In the three-dimensional world into which narrator Mr. Vane has been born and educated in the sciences, the action occurs in his upper-class ancestral home. The Library, dating back to before the invention of printing, occupies most of the first floor. Upstairs, through corridors and stairways that Vane has never explored, lies a garret in whose center is a small structure that in turn houses an antique mirror, which Vane learns by experience is the gateway to another world.