The book is the second part of the reliability textbook intended for students at technical universities. It contains the significant lectures of the introductory course, which are expanded in a way that they can also be used for independent reading and cover the reliability of complex systems, reliability models, ensuring reliability through the reproduction process, reliability tests and recommendations for the design of reliable products. Together with the first part, this volume is sufficient for entering into reliability issues and for acquiring the knowledge necessary for future in-depth study of reliability in case of interest or need.