WASHINGTON (WASHINGTON POST) - Former FBI director James Comey's memoir surged to the top of Amazon's bestseller list over the weekend after President Donald Trump attacked him in a string of angry tweets - and the book is not even published yet.

"A Higher Loyalty: Truth, Lies, and Leadership", due for release on April 17, had already been hovering in the top-20 in the months since it went up for pre-order.

But it got an unexpected bump when Mr Trump lashed out at Mr Comey, jumping from No. 15 on Saturday (March 17) morning to No. 1 by Sunday evening.

Mr Trump's decision to fire Mr Comey last May re-emerged in the news after Attorney General Jeff Sessions, acting on Mr Trump's stated wishes, fired former FBI deputy director Andrew McCabe last Friday night, shortly before his planned retirement.

Mr Trump tweeted his satisfaction with the move, accusing "Sanctimonious James Comey" of covering up "lies and corruption" in the FBI and leaking information to the media. He also blasted special counsel Robert Mueller's probe of Russian interference in the 2016 election, which was triggered by Mr Comey's ouster, saying there should never have been an investigation.

Among other things, Mr Trump criticised Mr Comey's practice as FBI director of writing memos about his conversations with the president.

"Can we call them Fake Memos?" Mr Trump tweeted.

Mr Comey is expected to discuss the substance some of his meetings with Mr Trump in the memoir, though almost nothing about the book's contents has been revealed publicly.

Mr Comey responded to some of Mr Trump's attacks on Saturday with what read like a subtle plug for the memoir.

"Mr President, the American people will hear my story very soon. And they can judge for themselves who is honourable and who is not," he tweeted.

As of early Monday morning, "A Higher Loyalty" still held Amazon's No. 1 spot, trailed by "Russian Roulette: The Inside Story of Putin's War on America and the Election of Donald Trump" by Michael Isikoff and David Corn.

Also in the top-10 were "A Wrinkle in Time", Madeleine L'Engle's fantasy novel that was recently released as a blockbuster film, and "A Brief History of Time" by Stephen Hawking, the renowned theoretical physicist who died last week.

There's never been any doubt about Mr Comey's book flying off the shelves. Intrigue has been building since last summer when his literary agents revealed that he had begun work on a manuscript.

Mr Comey has occasionally teased the book on social media. He recently tweeted a picture of himself recording the audiobook version, along with the caption "Lordy, this time there will be a tape", a reference to Mr Trump's false suggestion that he had recorded his interactions with Mr Comey.

The last inside account of the Trump administration, "Fire and Fury: Inside the Trump White House", created a frenzy in Washington when it dropped in early January. The book by Michael Wolff, which was riddled with gossip and inaccuracies, debuted at No. 1 on the New York Times bestseller list and remains the list's top-selling hardcover non-fiction book.

The publisher of Mr Comey's memoir, Flatiron Books, said Mr Comey will share "never-before-told experiences from some of the highest-stakes situations of his career" and offer an "unprecedented entry into the corridors of power".

Flatiron is taking extraordinary precautions to prevent any leaks, as Politico reported last week.

Rather than circulating print drafts, the publisher is using a password-protected electronic system allowing only those involved in the project to access it.

The book is also being stored under a code name, and warehouse workers who ship it will be asked to sign non-disclosure agreements, according to Politico.

A national book tour is scheduled for April and May. Mr Comey has also announced television appearances with ABC News's "20/20", CBS' "The Late Show With Stephen Colbert", and ABC's "The View".