"Electronic States in Crystals of Finite Size" offers a comprehensive analysis of electronic states in crystals characterized by their finite size. The theory, based on Bloch's theorem, is critically examined in this work, as it traditionally addresses the properties of infinitely large crystals. The author, Shang Yuan Ren, highlights the significant differences in electronic structure that arise when the size of a crystal decreases. These differences are not only theoretically important but also have practical implications for understanding materials in modern solid-state physics. The book is the result of years of research and reflection on the challenges posed by the application of periodic boundary conditions. It provides a valuable perspective for students and professionals engaged with the fundamentals of solid-state physics.