Hooked by Nir Eyal and Ryan Hoover explains how to build habit-forming products by leveraging the Hook Model, a four-phase process consisting of trigger, action, variable reward, and investment. The authors argue that by understanding and applying the Hook Model, companies can design products that become indispensable to users, creating strong user habits and achieving significant competitive advantage. The text provides numerous examples of successful products that have mastered habit-forming product design and explores the psychology behind user behavior, including the importance of internal triggers, motivations, rewards, and user investment. The authors also discuss the ethical implications of using manipulation to create habits and advocate for a more responsible approach to designing habit-forming products.