Ms. Khan disagreed. Over 93 heavily footnoted pages, she presented the case that the company should not get a pass on anticompetitive behavior just because it makes customers happy. Once-robust monopoly laws have been marginalized, Ms. Khan wrote, and consequently Amazon is amassing structural power that lets it exert increasing control over many parts of the economy.

Amazon has so much data on so many customers, it is so willing to forgo profits, it is so aggressive and has so many advantages from its shipping and warehouse infrastructure that it exerts an influence much broader than its market share. It resembles the all-powerful railroads of the Progressive Era, Ms. Khan wrote: “The thousands of retailers and independent businesses that must ride Amazon’s rails to reach market are increasingly dependent on their biggest competitor.”

The paper got 146,255 hits, a runaway best-seller in the world of legal treatises. That popularity has rocked the antitrust establishment, and is making an unlikely celebrity of Ms. Khan in the corridors of Washington.

She has her own critics now: Several leading scholars have found fault with Ms. Khan’s proposals to revive and expand antitrust, and some have tried to dismiss her paper with the mocking label “Hipster Antitrust.” Unwilling or perhaps unable to accept that a woman wrote a breakthrough legal text, they keep talking about bearded dudes.

Ms. Khan was born in London to Pakistani parents who emigrated to the United States when she was 11. She is now 29, an Amazon critic whose Amazon account is largely inactive, newly married to a Texas doctor who uses his Amazon Prime account all the time. Ms. Khan was supposed to move this summer to Los Angeles, where she had a clerkship with Stephen Reinhardt, the Ninth Circuit Court of Appeals judge and liberal icon, but he suddenly died in March. Instead, Ms. Khan is set to start a fellowship at Columbia this fall, and is considering other projects as well. There is no shortage of parties that want her advice on how to reckon with Big Tech.

“As consumers, as users, we love these tech companies,” she said. “But as citizens, as workers, and as entrepreneurs, we recognize that their power is troubling. We need a new framework, a new vocabulary for how to assess and address their dominance.”

At the S.M.U. library in Dallas, Ms. Khan was finding that vocabulary. These dead books, many from an era that predated the price-based era of monopoly law, were an influence and an inspiration. She was planning to expand her essay into a book, she said in an interview here in June.