Hooked: How to Build Habit-Forming Products by Nir Eyal — Summary, Key Ideas & Quotes

At the heart of the book is the 'Hook Model,' a four-step process that explains how products create user habits. The steps—Trigger, Action, Variable Reward, and Investment—form a loop that encourages repeated engagement. Eyal argues that successful products, from social media to fitness apps, seamlessly guide users through this cycle, making their use almost automatic over time.

Triggers are cues that prompt users to take action. External triggers are things like notifications or advertisements, while internal triggers are emotions or thoughts, such as boredom or loneliness. The most habit-forming products transition users from relying on external triggers to responding to internal ones, embedding themselves into users' lives at an emotional level.