In this book, both dynamical and kinematic X-ray diffraction is considered from a unified viewpoint, based on the fundamental laws that govern the interaction of X-rays with matter. The book is focused on basic concepts, but also covers in detail classical and modern applications, e.g., line broadening, texture and strain/stress analyses, X-ray mapping in reciprocal space, high-resolution X-ray diffraction and inelastic X-ray scattering. This unique scope, in combination with otherwise hard-to-find information on X-ray focusing components, X-ray interaction with phonons, coherent scattering of Mössbauer radiation and the interrelation between grain size-mediated and microstrain fluctuation-induced broadenings of X-ray diffraction profiles, makes the book indispensable for any serious user of X-ray diffraction techniques.