Quantum superposition is the most distinctive and puzzling feature of quantum physics. This book presents a clear and engaging discussion of the role of quantum superposition in diverse quantum phenomena. The author, whose extensive experimental and theoretical work helps elucidate these processes, also examines how macroscopic quantum coherence may be able to extricate physics from its most challenging quandary, the collapse of a massive degenerate star to a singularity in space in which the laws of physics break down. Explained by a physicist with a concern for clarity and experimental achievability, the extraordinary nature of quantum superposition will fascinate the reader not only for its apparent strangeness, but also for its comprehensibility.