During the Republic of China period, the country had entered an era of modern bookbinding, when hardcover books became relatively common. Emerging from the technical context of the Industrial Revolution, hardcover binding, referred to as “case binding” in English, emphasized speed and cost-effectiveness, which led to inherent structural weaknesses from its inception. Hardcover books that have survived to this day often exhibit structural problems such as detached covers and separation between the text block and the case, hindering their intended value. Drawing on contemporary Western conservation practices of case-bound volumes, this study took a hardcover dictionary as a case to illustrate a typical treatment process—including cleaning and disassembling, text block repair, case restoration, and reattachment of the case, in order to provide practical guidance and references for the structural repair of hardcover books of the Republic of China period. After the treatment, the dictionary’s historical appearance was largely restored, and its physical structure stabilized, enabling the book to meet the requirements of both academic research and long-term preservation.