Solids are formed from densely packed atoms. The interactions of these atoms are responsible for the emergence of magnetic, optical, thermal, mechanical and electrical properties of solids. Atoms in a solid can be arranged in a regular geometric pattern in a crystal or irregularly in an amorphous solid. The study of all these aspects of solids is approached from the field of solid state physics. It is a branch of condensed matter physics, which studies solids through the methods of electromagnetism, quantum mechanics, crystallography and metallurgy. The crystalline structure of materials is investigated using techniques of neutron diffraction, X-ray crystallography and electron diffraction. Solid state physics also delves into the study of quasicrystals, high-temperature superconductivity, strongly correlated materials, etc. It has applications in the development and use of semiconductors and transistors. This textbook presents the complex subject of solid state physics in the most comprehensible manner. Such selected concepts that redefine this field have been presented herein. Coherent flow of topics, student-friendly language and extensive use of examples make this book an invaluable source of knowledge.