This book is designed to be used by students taking a course in quantum mechanics or quantum theory. The prerequisites for this text are calculus and modern physics. The text has formal presentation, suitable for junior and senior levels, but is particularly appropriate for graduate level courses. It has been revised in response to changes and new work in the fields of physics. The text is separated into two parts - theory and applications. The instructor has the option of either interspersing the theory sections with the applications, teaching the book in the order presented or leaving out the applications altogether. A solutions manual is available.