The purpose of this study is to develop a valid and practical digital 3D books based on the mathematical understanding of a linear system with two variables. This study uses the ADDIE (Analysis, Design, Development, Implementation, and Evaluation) development model. Data were collected through semi-structured interviews, practicality tests, and validity questionnaires. The research samples were nine students and five mathematicians. The results of this study indicate that the use of digital 3D books is valid with a percentage of 92% and practicality with a percentage of 91.67%. In short, 3D books can be used in the learning process on a linear system of material with two variables and are easy to use for students. Teachers can facilitate the use of 3D books in mathematics learning classes, and students can also use this independently in learning.
3D book, Ausubel’s theory, mathematical understanding