Little moments in Rebecca Yarros' bestselling fantasy novel "Onyx Storm" could have huge implications for the rest of her "Empyrean" series.

The book, the third in a series, has sold 2.7 million copies in its first week, and provided yet another example of the romantasy genre’s staying power.

On the heels of the highly anticipated release of "Onyx Storm," Rebecca Yarros talks all things "Empyrean" with TODAY.com.

Rebecca Yarros released "Onyx Storm" on January 21, but readers are already looking forward to the next book in the "Fourth Wing" universe.

Rebecca Yarros’s ‘Onyx Storm is the fastest-selling adult novel in the past 20 years. The book, the third in a series, has sold 2.7 million copies in its first week and is topping every bestseller list.

Bestselling author Rebecca Yarros ' newest addition to The Empyrean series hit the shelves on Jan. 21, and less than two weeks later, the New York Times reported a stunning 2.7 million copies of Onyx Storm sold in its first week. This makes the third book in the series the fastest-selling adult novel in two decades, the outlet reported.

Bookshop manager Edward Woods refused to disclose how many copies had been sold in Romsey but said it had performed very well.