This revised and updated Fourth Edition of the text builds on the strength of previous edition and gives a systematic and clear exposition of the fundamental principles of solid state physics. The text covers the topics, such as crystal structures and chemical bonds, semiconductors, dielectrics, magnetic materials, superconductors, and nanomaterials. What distinguishes this text is the clarity and precision with which the author discusses the principles of physics, their relations as well as their applications. With the introduction of new sections and additional information, the fourth edition should prove highly useful for the students. This book is designed for the courses in solid state physics for B.Sc. (Hons.) and M.Sc. students of physics. Besides, the book would also be useful to the students of chemistry, material science, electrical/electronic and allied engineering disciplines. New to the Fourth Edition Solved examples have been introduced to explain the fundamental principles of physics. Matrix representation for symmetry operations has been introduced in Chapter 1 to enable the use of Group Theory for treating crystallography. A section entitled 'Other Contributions to Heat Capacity', has been introduced in Chapter 5. A statement on 'Kondo effect (minimum)' has been added in Chapter 14. A section on 'Graphenes' has been introduced in Chapter 16. The section on 'Carbon Nanotubes', in Chapter 16 has been revised. A Lesson on Group Theory, has been added as Appendix.