Years ago, I discovered Abebooks.com, a site that aggregates the inventories of used book sellers (hereinafter "Abe"). When I would discover an interesting book title, I would first go to Amazon and read the reviews. If that step further interested me, then I would go to Abe and compare the title's availability and price. Often I would buy the book on Abe, if a used one would suit. I got a better deal in terms of price, of course. But, in the process, I nicked the monolithic surface of Amazon, a tiny nick, of course, but a nick.
Several years ago, however, someone told me that Amazon acquired Amazon in 2008. (So much for our antitrust laws.) My nick, then, was reduced to whatever profit Amazon made on Abe's aggregation service because I settled for a used edition and not a new one. (Of course, Amazon now prominently offers used prices on its website.)
When Abe lists a used book for sale, however, it shows not only the availability and price of the title, but also the vendor among the used book sellers whom Abe aggregates. One may, then, go directly to the source and nick the Goliath with respect to the tiny price-profit that I would otherwise deliver by using Abe.
Yet the problem with Amazon is not only its price power over the book market, new and used, but also its exercise of that power in an attempt to "cancel" a title. That is, if the title is "controversial" in a way that Amazon dislikes, then it will not carry the title. Amazon will censor the book.
An example of that practice is the title When Harry Became Sally, Responding to the Transgender Movement (Ryan T. Anderson, 2018). Recently, I have become particularly interested in the Transgender movement, and decided to read that book.
I first looked on Amazon, and was not surprised that it still does not carry the title, new or used..
Then, I looked at Abe. It did not appear there either. The cancellation of the title appears to have extended to Amazon's control over Abe's aggregation part of the used book world.
However, by the time I started looking for a used copy of the forbidden title, thanks to Abe I had a list of favorite used book vendors who have an independent on-line presence. I went to one of them. Voila! There was the book, and I ordered it.