In this book, Jean Bricmont unravels the supposed riddles and mysteries of quantum mechanics and explains the fundamental principles of quantum theory to laypeople. He entertainingly emphasizes their paradoxical nature and clarifies the incredible amount of misconceptions, pseudoscience, and false philosophy that accompany many popular discussions about quantum mechanics. With minimal mathematics and technical language, he provides readers with answers to the most important conceptual questions associated with quantum mechanics: The question of determinism: Does quantum mechanics signal the end of a deterministic worldview? Does it explain or justify free will? The role of the observer in science: What role does the human being as a subject and observer play in the physical process?.