This book provides quick access to quantum mechanics without dealing with a true textbook that demands proper specialized studies in physics (and related mathematics) for about a couple of years. It consists of three parts: basic formalism, formal development, and ontological issues. The 70 figures are a crucial instrument for becoming acquainted in a representative way with abstract problems, and the 30 in-section boxes assist readers understand for difficult mathematical problems. The book offers a considerable number of clear and analytical treatments of what are considered the most difficult conceptual problems of the theory.