A modern presentation of theoretical solid state physics that builds directly upon Kittel's Introduction to Solid State Physics. Treats phonon, electron, and magnon fields, culminating in the BCS theory of superconductivity. Considers Fermi surfaces and electron wave functions and develops the group theoretical description of Brillouin zones. Applies correlation functions to time-dependent effects in solids, with an introduction to Green's functions. With 110 problems, the text is well-suited for the classroom or for self-instruction.