David Ogilvy, an advertising legend, highly recommends reading "Scientific Advertising" by Claude Hopkins, which he believes should be read seven times before engaging in marketing. The book, published in 1923, remains a timeless and influential guide to sales and marketing, with principles that continue to apply today. Three key pieces of advice from Hopkins are: (1) discovering what makes your product remarkable, (2) using psychology to sell products, and (3) being specific in your marketing claims. These approaches emphasize the importance of understanding consumer behavior, creating a compelling narrative around your product, and clearly communicating its unique benefits.