'Walmart (the incumbent leader in offline retailing) and Amazon (the attacking leader in online retailing) make up the most interesting business drama of our times. Will each stick to its current leadership role or will they emerge as dominant players in both roles? Nirmalya Kumar offers the best study that I have seen of these two world-wrestling competitors'

• PHILIP KOTLER, S.C. Johnson & Son Distinguished Professor of International Marketing, Kellogg School of Management, Northwestern University

Amazon and Walmart, with more than a trillion dollars in annual revenues combined, are the two largest companies in the world. They have not only redefined the retail industry- Walmart in the 1980s/1990s and Amazon since 2000-but have also been the benchmark for best practices in business (in terms of the use of IT, supply chain, data analytics and customer orientation).

In the coming years, Amazon will probably dethrone Walmart as the world's largest company, a position that Walmart has occupied for more than two decades. By examining these two companies and their business models in depth, Nirmalya Kumar elucidates the more general phenomenon of incumbents competing with disruptors (e.g., Volkswagen vs Tesla, Marriott vs Airbnb) as well as the move to omnichannel retail, where physical stores must coexist with online retailers.

Clash is a lucid, well-researched and eminently readable discourse on the future of retailing, the economics of e-commerce delivery models and whether its two largest players will collide head-on or coexist in strategic complementarity.