Abstract: In the late Classical period, the form of books in the West underwent a critical transition from scrolls to codices. However, scholars have not been able to give a convincing explanation for the reasons for a long time. The “Christian sentiment theory” which was proposed by C. H. Roberts and T. C. Skeeter and took a dominant position for many years, has also been questioned in recent years. The paper examines the material forms of the books, such as the bookbinding method, and layout of the codices between the 2nd and 3rd centuries with the methods of codicology and paleography, and the related academic tools such as Hexapla and Eusebian Canons. The results show that the actual needs of “expanding the capacity” and “ease of reference” of the codices that have been denied before, and the trend of canonization of early Christian texts reflected by them, are the important driving forces for the changes in the form of books.