For more than two years, downloadable audio has been the fastest-growing format in a book market plagued by overall flat sales. The Association of American Publishers reported that sales of downloadable audio in 2016 rose 19.7% from the previous year, to $640 million, and were 24.5% higher in the first four months of 2017 than in the comparable period in 2016.

In its most recent financial report, News Corp said that sales of downloadable audio rose 47% in its HarperCollins subsidiary in the fiscal year ended June 30, 2017, from sales in fiscal 2016. To meet the growing demand, HC CEO Brian Murray said, the company will put almost all of its new adult titles in digital audio.

Simon & Schuster and Penguin Random House both cited downloadable audio sales as an area of strength in the first half of 2017. With first-half digital audio sales 34% higher than in the same period of 2016, S&S CEO Carolyn Reidy said the company is upping its audio title output this year by 20%–25%.

Despite the continuing sales growth, it can be difficult to determine what is selling and in what numbers. News Corp gave a glimpse of the health of the market when it was discussing year-end results for fiscal 2017. The company pointed to sales figures for Mark Manson’s The Subtle Art of Not Giving a F*ck to highlight what it called “the rise of audiobooks.” Since its release, the book has had audio sales of more than 470,000 copies (compared to more than 490,000 in print). Though some were in CD format, the vast majority was almost certainly digital audio.

The Subtle Art was the top-selling audiobook this year through September 5 in Apple’s iBooks store. To get a sense of what else has been hot in downloadable audio this year, we asked Apple to provide us with the list of its top 20 sellers through September. The ranking shows a mix of frontlist and backlist books, with more nonfiction titles (13) than fiction (7). Self-help books were the most popular category on the list. And the iBooks audio bestsellers did not exactly match what was selling in print: only six of the top-selling books on BookScan’s print list also appeared on the iBooks list.

Top-Selling Downloadable Audiobooks in Apple’s iBooks Store, January 1–September 5

1 The Subtle Art of Not Giving a F*ck Mark Manson HarperAudio
2 The Four Agreements Don Miguel Ruiz Amber-Allen
3 The Shack Wm. Paul Young Windblown Media
4 The Dark Tower I: The Gunslinger Stephen King Simon & Schuster Audio
5 Hillbilly Elegy: A Memoir of a Family J.D. Vance HarperAudio
6 How to Win Friends & Influence Dale Carnegie Simon & Schuster People Audio
7 The Witness Nora Roberts Brilliance Audio
8 Rich Dad Poor Dad Robert T. Kiyosaki Brilliance Audio
9 Harry Potter and the Sorcerer’s Stone J.K. Rowling Listening Library
10 Extreme Ownership Jocko Willink & Babin Leif Macmillan Audio
11 The Handmaid’s Tale Margaret Atwood Brilliance Audio
12 You Are a Badass Jen Sincero Tantor Audio
13 The Art of War Sun Tzu
14 The Alchemist Paulo Coelho HarperAudio
15 Astrophysics for People in a Hurry Neil deGrasse Tyson Blackstone Audio
16 The Secret Words Rhonda Byrne Simon & Schuster Audio/Beyond
17 The Five Love Languages Gary Chapman Oasis Audio
18 Big Little Lies Liane Moriarty Penguin Audio
19 The Total Money Makeover Dave Ramsey Thomas Nelson on Brilliance Audio
20 The Power of Now Eckhart Tolle New World Library