Sen. Rand Paul continued his long-running feud with National Institute of Allergy and Infectious Diseases Director Anthony Fauci on Thursday, blasting the physician’s planned book as “science fiction.”

On Twitter, Paul posted a link to a news story about Fauci’s nonfiction book Expect the Unexpected being removed from presale on Amazon and Barnes and Noble’s websites, and wrote, “Oh, I don’t know. I think they should publish it. I love science fiction.”

National Geographic Books, which plans to publish Fauci’s book about the Covid-19 pandemic in November, told the Daily Mail that the book had been listed for presale accidentally and prematurely.

“The book was developed by National Geographic Books in connection with an upcoming National Geographic Documentary Film about Dr. Fauci,” the publisher said. “He will not earn any royalties from its publication.”

There’s no love lost between Paul, a Kentucky Republican, and Fauci, President Joe Biden’s chief medical adviser. The two clashed last September in a Senate hearing after Paul claimed that the Covid-19 infection rate in New York state, at the time low, was due to herd immunity.

“No, you’ve misconstrued that, senator, and you’ve done that repetitively in the past,” Fauci told Paul. “They got hit very badly.…In New York, it’s about 22%. If you believe 22% is herd immunity, I believe you’re alone in that.”

Michael Schaub is a Texas-based journalist and regular contributor to NPR.