Jonah Berger's book "Contagious," which explores the reasons why certain products, ideas, and behaviors become popular. Berger analyzes numerous case studies and research findings to identify six core principles, which he calls STEPPS, that drive social influence and word-of-mouth marketing. These principles are Social Currency, Triggers, Emotion, Public, Practical Value, and Stories. The text examines how these principles apply to a variety of situations, including the success of the hundred-dollar cheesesteak at Barclay Prime, the viral popularity of Blendtec's "Will It Blend?" videos, and the rise of Vietnamese manicurists in the United States.