The booktube community comprises individuals who share their literary experiences through videos posted on the YouTube platform. They are also book collectors who share their collections and their own subjective reasons for collecting books. Since their videos are published using tags, our focus was on the 'bookshelf tour' tag. This is a case study which utilized video analysis to investigate their classification criteria. We used the think-aloud protocols to collect the data. Content analysis was conducted, and the concept of classification was employed to understand the particular categories of private organization in their shelves and where these categories originated. Furthermore, we also considered studies related to book collections for interpreting the subjective connection between collecting and classification items in private collections. The results of the investigation highlighted three main aspects. Firstly, the desire to showcase their collection significantly influences their classification categories. Secondly, classification stands out as one of the primary activities of book collectors. Thirdly, the categories are influenced by their backgrounds and life stories, although many of them have been changing their classification considering their audience's opinion. When they make these classifications visible and explain their reasons for their choices, they also engage with their audience. In conclusion, we observed that when a classification scheme is based on the classifier's identity, it can lead to some instability in the categories. However, it also demonstrates how memory plays a crucial role in the retrieval process and how their worldview is reflected in these categories. Moreover, the digital environment influences on personal classification.