The symbolism of technology
The use of technology in the book is undeniably symbolic. Clay uses his technological skills as tools in his journey. He often uses computers to solve complicated problems, especially in the end when he decodes the cypher and solves the mystery of Manutius's manuscript. Technology in the novel represents the generational differences between Clay and his past-oriented employer.
The magic of the past
Technology is far from the hero in this story. Books, physical bookstores, and book clubs are all highly discussed, and Clay himself is defined by his work at a bookstore, discovering the magic of reading. Nevertheless, he is wired by his times, and he quickly solves the problems for the Unbroken Spine, but the implication is that although some people are happy to know the absolute truth of Manutius's scripts, others are really upset, because the solution of the riddle removed the magic of the quest.
The beauty of physical books and their readers
The plot seems like it is an allegory about the introduction of the internet and its effects on readers. Fewer people read actual physical books now, and the first half of the novel is about Clay interacting with the runes of an older way of life that predates his internet skills by a long, long time—a bookstore that never closes. The fact that even the title references the fact that the bookstore never closes seems to be an argument that although the internet is helpful, it will not eliminate books or people wanting to hold a physical book instead of enjoying audiobooks and ebooks (like Clay does in the novel).
Kat's role as symbol
The first time Clay tries to solve the bookstore's problems with the internet, he ends up being blessed with a new friend, Kat. This is an indication that he is heading the right way in life, and by the end of the novel, he has completed a journey, the journey of integrating his internet savvy to his employer's wisdom. Kat is a symbol for him to keep going, and when he takes a risk by following Penumbra to New York, she is with him, both physically and symbolically.
Google is involved in the plot. Although this technique of including real modern companies in fiction is highly controversial among writers, Mr. Penumbra's 24 Hour Bookstore, uses Google as a major component of the plot. Google employees take on the decoding project as a side project, helping Clay along in his journey. Interestingly, Kat is the one who connects Clay to Google. Here, Google is like a divine entity to Clay. Just as the pagans would have gone to the gods for rain, Clay goes to his internet gods for help. This is insightful commentary, but it's also a troubling comment on Millennial psychology.
