How Brands Grow: What Marketers Don’t Know by Byron Sharp is a marketing science book that challenges many of the traditional beliefs marketers hold about brand growth, customer loyalty, and advertising effectiveness.

Drawing on decades of research from the Ehrenberg-Bass Institute, Sharp argues that brands grow primarily by reaching more buyers rather than deepening loyalty among existing customers. He introduces concepts such as mental availability, physical availability, and distinctive brand assets, showing how successful brands make themselves easy to notice, remember, and purchase. The book challenges common marketing practices focused on niche targeting and customer retention, instead emphasizing broad reach and consistent brand recognition. With its evidence-based approach and practical insights, How Brands Grow has become one of the most influential books in modern marketing, reshaping how many businesses think about advertising, branding, and long-term growth.