An important part of this book is devoted to the description of homogenous systems, such as electron gas in different dimensions, the quantum well in an intense magnetic field, liquid helium and nuclear matter. However, the most relevant part is dedicated to the study of finite systems: metallic clusters, quantum dots, the condensate of cold and diluted atoms in magnetic traps, helium drops and nuclei. The book focuses on methods of getting good numerical approximations to energies and linear response based on approximations to first-principles Hamiltonians. These methods are illustrated and applied to Bose and Fermi systems at zero and finite temperature. Modern Many-Particle Physics is directed towards students who have taken a conventional course in quantum mechanics and possess a basic understanding of condensed matter phenomena.