It won’t be out for a month, but it’s already a best-seller.

James Comey’s “A Higher Loyalty: Truth, Lies, and Leadership” was the No. 2 book on Amazon’s best-seller charts Sunday morning, despite its not being available until April 17. The book also was in the Top 5 at Barnes & Noble’s pre-sales.

And Mr. Comey can likely thank President Trump for the surge in the book’s popularity over the past day.

According to CNN, the book was only No. 15 on Saturday — still high for a book only available now as a pre-order. But then Mr. Trump and Mr. Comey got into a Saturday Twitter spat and sales took off.

On Saturday, Mr. Trump, celebrating the Friday firing of Andrew McCabe as deputy FBI director, took at shot at Mr. Comey, whom he also fired in May. The president called Mr. Comey “sanctimonious” and complicit in “corruption going on at the highest levels of the FBI!”

Andrew McCabe FIRED, a great day for the hard working men and women of the FBI - A great day for Democracy. Sanctimonious James Comey was his boss and made McCabe look like a choirboy. He knew all about the lies and corruption going on at the highest levels of the FBI! — Donald J. Trump (@realDonaldTrump) March 17, 2018

That prompted Mr. Comey to tweet a few hours later that “Mr. President, the American people will hear my story very soon. And they can judge for themselves who is honorable and who is not.”

Mr. President, the American people will hear my story very soon. And they can judge for themselves who is honorable and who is not. — James Comey (@Comey) March 17, 2018

The book had been available as a pre-order for months, but after Saturday afternoon’s exchange, interest in Mr. Comey and his book went viral. By Sunday afternoon, the Comey tweet had been shared more than 112,000 times and liked by nearly 380,000 users.