This book describes a specific solution, known as Agile-SOFL, for bridging agile and formal engineering and discusses its benefits for realistic software projects. In this book, the author argues that formal engineering methods and agile approaches are complementary in ensuring high productivity while enhancing reliability. Agile-SOFL offers a highly practical and systematic method that strikes a good balance of efforts for enhancing both software productivity and reliability. Specifically, Agile-SOFL is characterized by five features: (1) systematic approach to constructing hybrid specifications for requirements-related faults prevention, (2) specification-based incremental programming for quality implementation, (3) specification-based inspection and testing for system validation, (4) automatic testing-based formal verification for the correctness of code, and (5) effective project management for high effectiveness and efficiency in applying Agile-SOFL. The objective of this book is to help readers learn the latest effective Agile development concepts and techniques and to take them to the point where they can easily apply Agile-SOFL to develop their own software systems with a high productivity and reliability. The reader can also considerably benefit from this book by learning many newly developed concepts and principles in fault prevention, fault detection, verification of code correctness, and efficient project management.