Friendship operates as a motif as well as being a central theme in the novel. Clay, in particular, makes a number of references to the idea of fellowship in popular culture. For example, the questing party is a foundational concept in the fantasy novels and role-playing games that Clay and Neel share an interest in and the recurring references to The Dragon-Song Chronicles are another reminder of this. Clay also describes Rosemary Lapin’s home as “the burrow of a bibliophile hobbit” (101), making a reference to the work of J.R.R.R. Tolkien whose The Lord of the Rings centers on the adventures of the Fellowship of the Ring. Similarly, when Clay, Kat and Neel have agreed to participate in Penumbra’s plan to make a digital copy of Manutius’s book, Clay refers to them as the “rebel alliance” of the popular Star Wars movies. Interestingly, the symbol of the Unbroken Spine itself, “two hands, perfectly flat, rising out of an open book” (8), suggests the open hands of friendship, a reading that is reinforced by Gerritszoon’s final message, which confirms the importance of his friendship with Manutius.