Library users should be conveniently interact with collections and be able to easily choose books of interest as they explore and browse a physical book collection. While there exists a growing body of naturalistic studies of browsing and book selection in digital collections, the corresponding literature on behaviour in the physical stacks is surprisingly sparse. We add to this literature in this paper, by conducting observations of patrons in a university library as they selected books from the shelves. Our aim is to further our understanding of patterns of behaviour in browsing and selection in physical collections.