"Hooked: How to Build Habit-Forming Products" is a book by Nir Eyal that explores the psychology behind why certain products capture users' attention and create lasting habits. It introduces the Hook Model, which consists of four key components: Trigger, Action, Variable Reward, and Investment. This model helps product designers understand how to engage users effectively. The book emphasizes the importance of creating products that not only fulfill users' needs but also encourage repeated use. By applying the principles outlined in the Hook Model, businesses can develop products that foster user loyalty and drive long-term engagement.