This book on solid state physics has been written with an emphasis on recent developments in quantum many-body physics approaches. It starts by covering the classical theory of solids and electrons and describes how this classical model has failed. The authors then present the quantum mechanical model of electrons in a lattice and they also discuss the theory of conductivity. Extensive reviews on the topic are provided in a compact manner so that any non-specialist can follow from the beginning.The authors cover the system of magnetism in a similar way and various problems in magnetic materials are discussed. The book also discusses the Ising chain, the Heisenberg model, the Kondo effect and superconductivity, amongst other relevant topics.In the final chapter, the authors present some works related to contemporary research topics, such as quantum entanglement in many-body systems and quantum simulations. They also include a short review of some of the possible applications of solid state quantum information in biological systems.