This book is written based on lecture notes covering three to four semesters of graduate courses in quantum mechanics. The author sets out by explaining the physical concepts of quantum mechanics, and then goes on to describe the mathematical formalism and present illustrative examples of the ideas and methods that serve to amplify points discussed in the text. Exercises, with solutions, are included.The chapters are not independent, but build on one another. Subjects range from the failures of classical theory to second quantization, including chapters on the Dirac theory and Feynman diagrams. The book is intended for use as a graduate level text as well as a reference.