"Contagious: Why Things Catch On" is a book written by Jonah Berger, published in 2013. The book is a comprehensive guide to understanding why some ideas and products become popular and how to create content that is more likely to spread.
In "Contagious," Berger explores the psychology of word-of-mouth and how it drives the spread of ideas and products. He identifies six key principles that make things more likely to catch on, known as the STEPPS: Social Currency, Triggers, Emotion, Public, Practical Value, and Stories.
Throughout the book, Berger uses real-world examples and case studies to illustrate his points and provides practical advice on how to apply the principles of contagiousness to marketing campaigns. He also covers topics such as online virality and how to use social media to increase the reach of content.
Overall, "Contagious" is a valuable resource for anyone interested in understanding why some ideas and products become popular and how to create content that is more likely to spread.