It’s not easy getting Megyn Kelly, Jon Stewart and Hunter Biden all rowing in the same direction.

Jake Tapper, and his new book, have managed to do just that.

Mr. Tapper, the longtime CNN anchor, has become one of the most talked-about figures in the media and political worlds in recent days because of “Original Sin,” a book released on Tuesday that he wrote with Alex Thompson, a political correspondent for Axios.

The book scrutinizes former President Joseph R. Biden Jr.’s mental and physical fitness while in office, and reports on his staff’s attempts to shield any decline from the public. The book’s subtitle claims that the efforts amounted to a “cover-up.”

“Original Sin” has received numerous positive reviews and appears to be a runaway sales hit. It has been on Amazon’s best-seller list for over a week, even before its release, and stood at No. 3 on Thursday. The book has also amplified debate about whether more blame should be placed on Democratic leaders, Mr. Biden’s staff and the press for not revealing more about the former president earlier.

“It’s hard to think of a book which has shifted the political dial to this extent in recent years,” Politico Playbook wrote on Tuesday.