According to Mrs. Elm, the Midnight Library is the physical embodiment of a state between life and death—an in-between state. The physical embodiment is different for each person; it’s reflective of a person and place with which the person felt comfortable. Mrs. Elm comforted Nora in the Hazeldene School library, where the two often played chess, so her in-between state is a library where Mrs. Elm is the guide; Hugo, another slider, visits a video store where his Uncle Philippe is the guide to his other lives.

The Midnight Library, and Mrs. Elm, are symbolic of quantum mechanics. Hugo mentions to Nora that, because humans are unable to grasp quantum space, the human mind makes sense of the quantum mechanics of an in-between state by projecting a comforting symbol.

Nora thinks of herself as a black hole, which is a “dying star, collapsing in on itself” (13). Nora first sees the black hole imagery at the newsstand before she attempts suicide, and she attributes her failures to a dying, collapsing life. The black hole imagery is on the cover of a National Geographic issue that appears in several of Nora’s lives as a motif for failure, but also as an overarching symbol for despair.