Definitely not required reading for all designers but a pleasant and useful one for some of them nevertheless
For some people there comes a time when they have spent more than five decades in their career and they can have a deep look at various projects they have accomplished, and talk about the common themes, as well as the distilled lessons they learned throughout a lifetime. If they also happen to be good writers as well as having lots of very successful achievements in industrial settings as well as academic and personal ones, then the reader of their work is lucky indeed. The Design of Design is one such book, at least for some readers.
Even though the book has many qualities, I consider it important to warn the casual reader: You are facing a book full of deep principles and abstractions. No matter how many concrete examples you may encounter in different chapters, the discussion of principles behind those examples are not to be taken lightly, Brooks often refers to the works of Christopher Alexander, an architect, designer, mathematician and cognitive scientist, not only famous for his work in architecture and design, but also for inspiring the famous “Design Patterns: Elements of Reusable Object-Oriented Software” book as well as his non-mainstream writings. This alone should be enough evidence for the knowledgeable reader that this book aims to be something more than a passing attempt at discussing a few design principles.
Apart from that warning, I can say that, if you are a software or computer engineer with more than 9-10 years of experience under your belt, during which you struggled with big, complex and collaborative projects as well as giving some serious thought to design issues, you might very well enjoy the book and even want to read it twice, reflecting on how themes from very different areas such as computer hardware design, complex software design and a summer-house design come to have some surprising common points.
If you are not a very experienced designer or engineer, someone junior with only a few years of experience, then I suggest you read The Mythical Man-Month: Essays on Software Engineering, Anniversary Edition (2nd Edition) and then come back to The Design of Design after a few years. After all, the timeless discussions regarding the fundamental issues of designing complex systems and structures will not change very much in a few years.