The Toronto Public Library has become the first library in the world to lend more than 20 million ebooks, the library announced this week.

“Our customers are very engaged with the digital book collection,” said Maria Cipriano, the library’s senior collections specialist responsible for ebooks. “As we find out any time it goes down, it becomes an emergency.”

The library, which announced the milestone Wednesday, started its first digital collection in 2007, which included books such as Astrology for Dummies, a book on Joan of Arc, and 17 travel guides.

By 2017, the collection included more than 170,000 titles, which were borrowed more than 4.6 million times that year alone.

Cipriano shared a list of the 20 most popular ebooks borrowed. The Girl on the Train comes in at No. 1, borrowed 19,156 times. Numbers two to five are The Goldfinch (borrowed 13,876 times), Gone Girl (borrowed 12,633 times), The Cuckoo’s Calling (borrowed 10,237 times), and You Are a Badass (borrowed 9,916 times).

“I see these trends ... come and gone, but you know we have these enduring classics and modern classics that will go out forever,” Cipriano said. “Like the modern classic, The Goldfinch. It’s gone out a tremendous number of times, and any time I feature it on our landing page, it goes out again. Some of these books are going to be around for a long time.”