Book excerpt: More than 70% of customers consult online reviews and take them very seriously. A disgruntled customer on Yelp might have more clout than a guidebook, magazine, or newspaper. This review-driven marketplace terrifies many businesses. But some have learnt to navigate and profit from customer reviews. Bill Tancer takes readers on a fascinating journey inside that world, to find out why one Los Angeles barber advertised his one-star reviews and how one scrappy hotel became the highest rated in London. Tancer's fascinating stories and data-driven research reveal how sites like Yelp and TripAdvisor are changing the way we interact and show how business owners can leverage online reviews to find greater success.