In a talk at DigiCon 2016 on Tuesday, Rakuten Kobo CEO Michael Tamblyn laid out the case for continued growth in e-books at time when print seems resurgent.

Tamblyn offered an overview of Kobo’s global e-book retailing operations (“27 million readers, most of whom are not in the U.S.”), examining who those readers are and how to “get people to read more.” According to Tamblyn, selling the first book to a consumer “is hard. Selling them the next 100 books is easy.” And the more time users spend using Kobo products, the more data Kobo is able to collect to learn more about users’ reading habits.

What Kobo has learned, he said, is that while much of today’s book marketing is focused on millennials aged 18-34, Kobo’s “sexiest” customer is actually an older reader aged 50 to 70—and that’s for both digital reading and print titles.

“Fifty, 60, and 70-year-olds drive e-book sales in most countries,” he said. “[They] love digital but still buy print books. They read a lot so they accept e-books but still love [print books].”

While young readers are more responsive to online marketing and to social media promotions, Tamblyn said Kobo’s best customers continue to be older readers “who are still influenced by old media, such as book reviews, and by word of mouth.”

Tamblyn also discussed data on the differences between selling fiction and nonfiction. Fiction, he said, has a relatively well-known sales breakdown, with 50% of online fiction sales coming from online search—meaning the readers know exactly the book they want—25% coming via retailer merchandising, and another 25% coming from recommendations generated by the retailer’s site.

Nonfiction, however, “doesn’t work that way,” Tamblyn said. “Nonfiction just doesn’t have the same mojo as fiction.”

Fiction readers, he said, tend to be repeat buyers in the same category and will follow authors or series that they have liked in the past. Nonfiction readers, however, may have enjoyed a particular biography of a historical figure such as Winston Churchill, but they won’t necessarily want to read another book about him. Indeed, while fiction readers tend to finish the books they start, most nonfiction readers don’t generally finish a book, even if they loved it.

And while fiction readers often have a definite notion of what they want to read, nonfiction readers seem to “Want something they didn’t expect to buy. They like to look around for something to jump out at them.”

The goal of harvesting this kind of data on reader habits, he said, is to “create a kind of online bookstore that is constantly rearranging itself tirelessly based on its readers, in a way that no physical bookstore can do.”

But Tamblyn was also quick to caution that the emerging book marketplace is not a competition of “retailer vs. retailer,” but is actually “books and reading against everything else.”