This is a textbook on non-relativistic quantum mechanics that emphasizes clarification of the nature of the basic postulates and the interpretation of the theory. It contains special material, often only accessible in scientific journals, on bound states, scattering theory, and both analytical and approximation techniques. Applications to many branches of physics are given. Among the topics covered are one-dimensional problems, angular momentum, two-particle systems, symmetry transformations, collision theory, the WKB method, and stationary and time-dependent perturbation and variational...