The book argues that you cannot draw UML diagrams linearly (Requirements -> Analysis -> Design -> Code). Instead, it maps every single UML diagram to a specific phase of the Unified Process:
Jim Arlow and Ila Neustadt succeeded because they treat UML 2 not as a bureaucratic requirement, but as a for the Unified Process. Whether you acquire the physical book, the official eBook, or—if you are diligent—a legacy PDF, the patterns inside have not aged a day. The book argues that you cannot draw UML