"Hacking Growth" by Sean Ellis and Morgan Brown is a guide for growing companies based on the principles of growth hacking. The book emphasizes the importance of experimentation and data-driven decision-making in the growth of any product or service. It also stresses the significance of cross-functional collaboration between marketing, engineering, product, and design teams. The book provides frameworks and strategies for building a must-have product, activating new users, retaining customers, and maximizing revenue. It includes numerous case studies and real-world examples of companies that have successfully leveraged growth hacking to achieve rapid growth.