Soft X-Ray Spectroscopy of Astrophysical Plasmas (Steven M. Kahn): Classical and Quantum Radiation Theory -- The Structure of Multi-Electron Atoms -- Electron-Ion Collisional Processes -- Discrete Line Diagnostics -- Concluding Remarks -- Instruments for Nuclear Astrophysics (Peter von Ballmoos): Introduction -- Interaction of High-Energy Photons with Matter -- Detectors -- The Instruments for Nuclear Astronomy -- Hard X-Ray and Gamma Ray Spectroscopy (Rashid Sunyaev and Sergey Sazonov): Fundamentals of Compton Scattering -- Comptonization in Infinite Homogeneous Media -- Comptonization in Bounded Plasma Clouds -- Interaction of X-Rays with Partially Ionized Media -- 6.4-keV Fluorescent Emission from Molecular Clouds in the Galactic Center -- X-Ray Emission from Supernova 1987A -- Accretion onto Black Holes and Neutron Stars.After three decades of intense research in X-ray and gamma-ray astronomy, the time was ripe to summarize basic knowledge on X-ray and gamma-ray spectroscopy for interested students and researchers ready to become involved in new high-energy missions. This volume exposes both the scientific basics and modern methods of high-energy spectroscopic astrophysics. The emphasis is on physical principles and observing methods rather than a discussion of particular classes of high-energy objects, but many examples and new results are included in the three chapters as well.