This book puts emphasis on developing the basic ideas behind the different approaches to non-equilibrium thermodynamics and on applying them to solids. After a survey about different approaches an introduction to their common fundamentals is given in the first part. In the second part the mechanical behavior of special materials such as viscoelasticity, viscoplasticity, viscoelastoplasticity, and thermoplasticity are discussed. The third part is devoted to extended thermodynamics. The basic ideas, phenomenological as well as microscopical, are reviewed and applied to thermo- and viscoelastic materials. Electromagnetic solids showing dielectric relaxation, such as ceramics, showing electromagneto-mechanical hysteresis and superconductivity are treated in the fourth part. In the last part stability with regard to constitutive equations is investigated. Especially stability of quasi-static processes and of elastic-plastic systems are discussed.