When librarians enthuse about classification systems to those uninitiated in the profession, there is not a small chance they will be met with words to the effect of “who cares?” Yet, as American journalist Susan Orlean reminisces, a reader with classmark in hand scanning library shelves for the matching letters and numbers from the catalogue they recently jotted down (or more likely today, screenshotted) will often happily encounter related neighbouring books they might have never heard of and did not know they wanted. This possibility for serendipitous discovery comes from a process of classification: defining a book’s subject and representing it with a brief, alphanumeric code. The outcome: a singular, linear sequence guiding readers through the universe of knowledge. Our recent survey of Queens’ students found that around a quarter of undergraduates browse library shelves to find books to read for their studies, and so, consciously or otherwise, interact with classification systems.