The guessing game began a few days ago, when an anonymous, untitled book scheduled for July 9 -- “4C Untitled Flatiron Nonfiction Summer 2023” - had Taylor Swift fans so convinced she had written a memoir that they made it a bestseller. By Thursday, the Swift rumors had been refuted and the mystery resolved: Flatiron Books announced the upcoming release of a book by another musical powerhouse, BTS.