Book excerpt: A complete explanation of quantum mechanics, from its early non-relativistic formulation to the complex field theories used so extensively in modern theoretical research, this volume assumes no specialized knowledge of the subject. It stresses relativistic quantum mechanics, since this subject plays such an important role in research, explaining the principles clearly and imparting an accurate understanding of abstract concepts. This text deals with quantum mechanics from its earliest developments, covering both the quantum mechanics of wave fields and the older quantum theory of particles. The final chapter culminates with the author's presentation of his revolutionary theory of fundamental length--a concept designed to meet many of quantum theory's longstanding basic difficulties.