Hooked

Hooked: How to Build Habit-Forming Products by Nir Eyal, published in 2014, is the foundational text on Behavioral Product Design. Eyal distills how the world's most engaging digital products — from Instagram to Slack — keep users coming back through a deliberate four-stage Hook Model: Trigger, Action, Variable Reward, and Investment. The book has become required reading for product managers, growth teams, and founders.

For executives building consumer or B2B products, Hooked provides a rigorous framework for engineering retention rather than relying on it. Eyal also addresses the ethics of the model directly, introducing the Manipulation Matrix — a tool leaders can use to distinguish between products that genuinely improve users' lives and those that simply exploit psychological vulnerabilities. The book is as much about responsible product strategy as it is about engagement mechanics.