The mystery behind Flatiron’s big summer book has been resolved.

The publisher confirmed that it will publish an oral history of the phenomenally popular K-pop band BTS on July 9, the New York Times reports.

The revelation comes after days of speculation on TikTok over the book that was listed in Flatiron’s catalog as 4C Untitled Flatiron Nonfiction Summer 2023.

The TikTok account of Good Neighbor Bookstore in the New York village of Lakewood kicked off the drama with a since-deleted video speculating that the book would be a memoir by pop megastar Taylor Swift. The store’s owner noted that the book is 544 pages, and that those digits add up to 13, Swift’s lucky number, and that Flatiron had said the book “has a global appeal and skews towards a younger audience.”

Swift’s fans on TikTok ran with the theory, but the next day, a competing one surfaced, from fans of BTS, who claimed that the band was actually behind the mystery book. They pointed out that Flatiron planned to reveal the author(s) of the book on June 13, the anniversary of BTS, and that July 9, the date of the book’s release, is the day dedicated to the appreciation of the BTS ARMY, the band’s vast fan club.

On Thursday, Flatiron confirmed to the Times that the book is indeed related to the boy band. Beyond the Story: 10-Year Record of BTS is written by the band’s members and journalist Myeongseok Kang, and translated by Anton Hur with Clare Richards and Slin Jung.

Swifties might be disappointed, but that hasn’t dampened enthusiasm for the book. As of Friday morning, it was the No. 1 bestselling book on the Amazon and Barnes & Noble websites.

Michael Schaub, a journalist and regular contributor to NPR, lives near Austin, Texas.