Book publishing has reached a point of what could be called stable insecurity. The steep fluctuations of the post-Kindle years, in which rapid e-book growth seemed poised to upend the industry, have settled—for traditional publishers, at least, e-book sales have sharply declined over the past few years. Print books, thanks in part to pricing strategies that disincentivize e-book purchasing, have inched upward. Though hobbled, the industry’s most important retailer, Barnes & Noble, is still standing, while a rise in the number of indie bookstores has provided an important feel-good-story. Literary fiction is in crisis—sales are down 25 percent since 2012—and the bestseller list is dominated by books with “Trump” and/or “Russia” in their titles, but as a whole the industry has escaped what used to be a constant sense of crisis.

And if the overall picture is “meh,” there are some bright spots. The brightest might be the audiobook boom that’s taken place over the last few years. Earlier this month the Association of American Publishers reported that net audiobook revenue surged 29.5 percent in 2017, compared to the previous year. For some writers, audiobook sales are outpacing other formats. As reported by The New York Times in June, John Scalzi’s 2014 novel Lock In sold 22,500 hardcovers, 24,000 e-books, and 41,000 audiobooks. The print book’s unquestioned supremacy ended a decade ago; now we’re in an environment in which print books, ebooks, and audiobooks are of equal importance for many authors and publishers.

From a revenue standpoint, this is very good news for publishers. But it’s complicated. Audiobooks are dominated by Audible, which is owned by Amazon. Amazon effectively has the market for both e-books and audiobooks cornered. And Audible is working hard not just to maintain its market share but to grow it, expanding its production of original work and signing big name authors like Michael Lewis to exclusive contracts. When considered against the backdrop of Amazon’s ambitions to become an entertainment powerhouse, there are reasons for publishers to go back to being nervous.

Technological change is at the heart of the audiobook craze. Once unwieldy—the audiobook for George R.R. Martin’s A Game of Thrones consists of 28 CDs—the smartphone made even the longest, heaviest book portable. The larger demand for audio storytelling (Audible also produces podcasts) has also played a role. But Audible’s particular success is largely tied to Amazon’s market dominance. Amazon owns electronic bookselling in general, so it’s no surprise that it would own electronic audio-bookselling as well. (It is also helped by its subscription service, which at $14.99/month essentially amounts to an audiobook at half price.)

The signing of Lewis last month tells us a lot about how far Audible has come, and how far it still has to go. Lewis is a nonfiction superstar, whose books, like Moneyball and Liar’s Poker, reliably sell hundreds of thousands of copies. Amazon has been publishing original fiction and nonfiction for years, but it has struggled to compete with traditional publishing houses when it comes to big names. Instead, Amazon’s print divisions have largely exploited inefficiencies, publishing books (like works in translation) that are neglected by the large New York publishing houses.

Audible’s success has begun to open that up. Lewis’s deal will encompass four Audible Original stories, the kind of longform magazine work he traditionally has produced for places like Vanity Fair. Lewis joins Tom Rachman (whose short story collection Basket of Deplorables was written for Audible before being published in print last summer), Robert Caro (whose bite-sized On Power was produced by Audible last year), Margaret Atwood (who created a special edition of A Handmaid’s Tale exclusively for the company), David Spade (whose forthcoming memoir will be released as an Audible Original next month), and Scalzi. Audible also crowed earlier this year about acquiring the rights to snowboarder Shaun White’s memoir, which it will release as an enhanced audiobook before Houghton Mifflin Harcourt publishes a print edition.

Audible isn’t exactly a giant-killer yet, but it is putting out an intriguing mix of content, one that—if you squint a bit—resembles the work being done by the publishing houses Audible simultaneously is partnering with and competing against. Audible is emphasizing its strengths while essentially taking what it can get from big-name authors—it’s a smart, patient strategy that is yielding results. We’re still a long way off from an author of Lewis’s caliber signing an Audible exclusive contract for an actual book, but that seems plausible for the first time. Earlier this year, The Wall Street Journal reported that Audible was pursuing deals where it would acquire audio, print, and electronic rights.

Print publishers have responded by spending more on audiobook production. Last year, Penguin Random House’s audiobook of George Saunders’s Lincoln in the Bardo featured a cast of 166, including Ben Stiller, Lena Dunham, Julianne Moore, and Don Cheadle. Competition between Audible and publishers has been a rare boon for authors, with audio advances on the rise. But publishers have good reason to be concerned about Audible’s expansion, and its growing ability to attract top-shelf talent.

As Alexandra Alter noted in The New York Times last month, Lewis’s deal suggests that Audible is looking for ways to push publishers out of the audio realm, in order to grow its own profit margins (which take a hit, thanks to its bargain-priced subscription service). For publishers, audiobooks are important subsidiary rights that can be sold to help recoup the risk that they take on when they sign an author; given the high margins that they command, they are also increasingly important to publishers’ bottom lines, which are, as always, tenuous.

But it also points to Amazon’s larger goals. The company is embracing content creation at every level to woo subscribers, from its reported $1 billion Lord of the Rings TV show to its increased spending on original audio content. Years ago, when Amazon started publishing books, there was a worry that the company would undermine the publishing industry at every level—from book production to sales. That day never came. But now, with the rise of Audible, Amazon finally has a content production arm that can rival the large New York publishing houses.

Correction: An earlier version of this piece misidentified the sales of John Scalzi’s Lock In as the sales of the author’s later novel, The Dispatcher.