The phrase refers to a hypothetical continuation of a well-known fantasy saga. The initial series concluded with book 14; thus, ‘book 15’ indicates a potential, and currently nonexistent, extension to the original narrative. Discussion around this concept often involves fan speculation, authorized sequels, or possible spin-offs.
The significance lies in the enduring popularity and the rich universe established by the author. The possibility of further exploration of that universe generates considerable interest. Furthermore, the hypothetical continuation carries the benefit of providing additional narratives and characters for devoted readers to enjoy, expanding the established lore and potentially introducing new themes or perspectives.