This textbook addresses students, professionals, lecturers and researchers interested in software product line engineering. With more than 100 examples and about 150 illustrations, the authors describe in detail the essential foundations, principles and techniques of software product line engineering. The authors are professionals and researchers who significantly influenced the software product line engineering paradigm and successfully applied software product line engineering principles in industry. They have structured this textbook around a comprehensive product line framework. Software product line engineering has proven to be the paradigm for developing a diversity of software products and software-intensive systems in shorter time, at lower cost, and with higher quality. It facilitates platform-based development and mass customisation.The authors elaborate on the two key principles behind software product line engineering: the separation of software development in two distinct processes, domain and application engineering; and, the explicit definition and management of the variability of the product line across all development artefacts. As a student, you will find a detailed description of the key processes, their activities and underlying techniques for defining and managing software product line artefacts. As a researcher or lecturer, you will find a comprehensive discussion of the state of the art organised around the comprehensive framework. As a professional, you will find guidelines for introducing this paradigm in your company and an overview of industrial experiences with software product line engineering.