“There was a little bit of art to the science of doing this,” said Andrew Medlar, who runs the library’s book-buying operation and led the team that worked on the list.

Because the library’s central circulation system only goes back several decades, the team used recent circulation data, best-seller lists, archives from the National Book Awards and Newbery Medals, and the library’s best-of lists to figure out what books were most beloved by patrons.

“The idea was to see what has been generally popular out in the world,” Medlar said. “We wanted to start from the love of books and the love of reading rather than the numbers.”

Books that had been in circulation longer had a clear advantage, as they had more time to rack up checkouts. “To me it’s amazing that ‘Harry Potter’ made it onto this top 10 list,” Medlar said, considering the book was published a little more than 20 years ago. The oldest book on the list, “How to Win Friends and Influence People,” was only one slot above “Harry Potter” despite being around since 1936.

The list also includes an honorable mention: “Goodnight Moon,” by Margaret Wise Brown.

“We know that book is incredibly popular and has a lot of checkouts,” Medlar said, but because of the tastes of Anne Carroll Moore, an influential children’s librarian at the time of the book’s publication, in 1947, “Goodnight Moon” was not added to the collection until 25 years later. Every other book on the list was added to the collection the year it was published.