The hottest book on Amazon has no cover or title, but readers have sent it to the No. 1 spot anyway.

There’s a reason for that: It’s the next book by Rebecca Yarros, author of the phenomenally popular Empyrean series of romantasy novels.

The book, set for publication on Sept. 29 by Entangled, has no description on its Amazon page, where it is listed as “Untitled Empyrean (Not Book Four).” That means it won’t be the next installment in the series that began in 2023 with Fourth Wing and continued with Iron Flame and Onyx Storm. All three became massive bestsellers and are being adapted into a television series by actor Michael B. Jordan’s production company.

On Instagram, Yarros addressed the book’s ascent up Amazon’s bestseller list, writing, “Okay, so I had this little idea about a year ago to drop a surprise for you guys. But then you not only found it as soon as my publisher put it on preorder, but shot it straight to number one on Amazon without a cover, title, or even a vague idea of what might be coming your way!?!? You’ve rendered me speechless.”

She clarified that the book is not the next official installment in the Empyrean series but assured fans that the fourth novel is still in the works.

“And no, this hasn’t altered book 4’s timeline in the least,” she wrote, adding that “this is NOT the upcoming graphic novel.”

Michael Schaub is a contributing writer.