The textbook "Design of a Portfolio Management System for Software Line Development: Merging the Gap between Software" by Michael Lang offers a comprehensive analysis of the challenges and opportunities associated with software line development in companies. In an era where software plays a central role in nearly all industries, the need for companies to pursue innovative approaches and continuously reinvent themselves is becoming increasingly clear. The book highlights the importance of reusability and modularity in software development and presents software line development as a promising concept that originally stems from the automotive and fashion industries. Lang discusses the integration of software lines into companies' product portfolios and emphasizes that the success of these approaches heavily depends on their implementation. This work is aimed at professionals and students who wish to gain a deeper understanding of modern software development methods and their strategic significance in the business world.