Decision-making processes are something very personal and have many facets. Markus Wessler addresses well-known as well as unusual aspects of decision theory in this textbook, attempting to bridge the gap between the two poles of rationality and intuition. Starting from game theory, a central area in economics, the author connects it to cooperative and other concepts that are now applied in practice. He aims to awaken readers' understanding of the fundamental issues surrounding decisions and to inspire them with the possibilities of mathematics. By developing theoretical concepts based on concrete problems and in an understandable language, the book is also suitable for students who have had little exposure to mathematics so far. The book is enriched with exercises and prompts for further thought.