This book offers an introductory course in solid-state physics, covering both fundamental theoretical concepts and their applications to describing the physical properties of solids and the processes occurring within them. It addresses key topics such as the theory of crystal lattices (including the role of defects, thermal properties, and diffusion), essential knowledge from atomic physics and quantum mechanics, and, based on these, the electronic theory of solids. The text also explores how this theory is applied to analyze the electrical and magnetic properties of dielectrics, ionic crystals, semiconductors, and metals. Written in a clear and accessible style with minimal mathematical complexity, the authors skillfully and up-to-date explain many intricate and subtle issues using illustrative model representations. This book is recommended as a supplementary resource for university students and students of technical institutes beginning their study of solid-state physics or its specific sections. It will also be valuable for young professionals, educators in the field, and researchers in related scientific disciplines seeking to familiarize themselves with the core concepts and methods of solid-state physics.