How does O'Connell use specific word choice to mirror the themes of the text?

When O'Connell gets locked inside a bomb shelter-type structure during his visit to PointX, he uses purposeful word choice in order to reflect the themes of loss, death, and finality associated with the topic of the book. Describing the sound of the door closing behind him, he states, "It was an apocalyptic sound, and I was both unnerved and exhilarated. The darkness, too, was absolute, an annihilation of the very concept of light" (55). The use of the term 'annihilation' here mimics O'Connell's deep dubiousness about the wisdom of locking ourselves away from life in order to preserve our lives.