Read: What Amazon thinks you’re worth

And Amazon Publishing is a culture-making juggernaut, even if the literati don’t much think about it. According to Peter Hildick-Smith, the CEO of the book-industry analysis firm the Codex Group, roughly 25.5 million U.S. households bought books in the past month, and fully a quarter of those households use Prime Reading, a feature of Amazon Prime that allows subscribers to borrow 10 items at a time from a catalog of 1,000 ebooks, magazines, and other media, including the tech giant’s originals.

Prime Reading is far from Amazon’s only reading subscription service. Kindle Unlimited, a similar program, costs an extra $9.99 and offers a wider selection of millions of titles.** The Prime Book Box for children includes a selection of age-appropriate books delivered regularly for $19.99. Amazon First Reads allows members to download a book a month earlier than the unsubscribed public for no extra cost. Often, First Reads are—you guessed it—Amazon Publishing titles, and they rocket up the Amazon best-seller charts as soon as they’re made available; A Fire Sparkling and What You Did both topped the charts in early July despite being due out August 1.

And then there’s Amazon’s 19 brick-and-mortar stores around the country, which sell print copies of Amazon Publishing titles, produced via a sophisticated print-on-demand operation.*** All told, these services overlap to create an ecosystem with the same aim and model as Prime: to lock customers into a regular subscription that shifts the center of their purchasing gravity to Amazon. The company’s distribution mechanisms then allow it to push its own titles to subscribers to keep them happy with their membership—not unlike how Netflix’s recommendation algorithm tells you to watch Netflix-produced films.

Amazon Publishing is still a relatively small fry: According to Hildick-Smith, it puts out 1,100 titles a year, compared with the 1,500 to 2,000 a large publishing house such as Simon & Schuster might publish. Estimating sales for those 1,100 titles is difficult, according to experts, because the tech giant doesn’t disclose ebook sales numbers for its original books, and its proprietary methods of distribution obscure those figures from the third-party researchers who determine best-seller lists.

Grace Doyle, the editor who oversees the Amazon Publishing mystery/thriller imprint, Thomas & Mercer, and the science fiction/fantasy label, 47North, says the subsidiary looks at three things when measuring the success of a title: the book’s sales, the number of people who actually read it (Amazon maintains a “most read” chart, measured by ebook pages turned), and whether the company can expect more books to come from its relationship with the author. She said again and again in our interview that her goal was to maintain partnerships with authors for as long as possible, which often results in publishing series, especially for the thrillers and mysteries that do so well with ebook readers.