Soren is a devout Mormon who dies in middle age from brain cancer, only to awaken in a Zoroastrian version of Hell shaped like an infinite library. He faces a profound crisis upon learning his lifelong religious beliefs were incorrect. Placed in an incomprehensible situation where he must find the book of his life story to escape, he tries to maintain his sanity while facing the overwhelming nature of eternity.

Dire Dan is an extremist who establishes a violent religious cult within the afterlife. Claiming to have received a direct vision from God, he instructs his followers to ruthlessly torture and terrorize other residents. His actions permanently disrupt the peaceful societies that have formed over the centuries.

Rachel is a resident of the infinite library and an active member of the society's university dedicated to studying discovered texts. She openly shares her feelings of exhaustion regarding the library's massive scale. Her connection with Soren provides temporary relief from the monotonous eternity of Hell.

Biscuit is a formerly unhoused Vietnam War veteran who arrives in the library at the same time as Soren. He carries deep trauma from his past and struggles with his mental health in his new environment. Desperate to find purpose in his surroundings, he obsesses over a randomly discovered book containing the words "sack it."

Xandern is a minor Zoroastrian divinity who processes the dead upon their arrival in the afterlife. He casually informs people that their lifelong beliefs were wrong and assigns them to temporary hells based on their personalities. He maintains a highly bureaucratic demeanor in the face of human terror.

Betty is a woman from Mississippi who meets Soren shortly after his arrival in Hell. She bonds with him over their shared grief of being permanently separated from their earthly spouses.

Sandra is an inhabitant of the library who shares a romantic connection with Soren during his first century. She observes Soren's growing closeness with Rachel with obvious jealousy.

Wand is a woman whom Soren encounters while plummeting through the library's endless central abyss. Desperate for contact after extreme isolation, she clings to Soren to establish a brief but highly meaningful physical bond.

Master Took is an analytical resident of the library who dedicates his time to calculating its exact dimensions. He determines the library contains an incomprehensible number of books.

Elliott is a World War II veteran who arrives in the library alongside Soren. His military background allows him to empathize with Biscuit's wartime trauma when others cannot.

Dolores is an inhabitant of the library who is part of Soren's initial group. She expresses clear anxiety about mental health and the psychological toll the library takes on its residents.