This introductory treatment begins with an overview of the basic ideas of perturbation theory, addressing the conditions under which the theory may be set up and the various forms of perturbation expansions. Subsequent chapters explore diagrammatic methods in terms of linked cluster theorem and general formulas as well as rearrangement methods. Techniques of solving the t-matrix equation and other equations that arise in the nuclear many body problem are examined in terms of approximate methods, and the intuitive reasoning behind each of them is given. The text's final chapter collects other methods of approaching the many body problem and shows how they may be compared with those of previous chapters. Suitable for advanced undergraduates and graduate students, this volume features many helpful citations to literature on the subject, and a list of main symbols has been appended to each chapter for easy reference.