President Trump delivered a video message to reporters during White House press secretary Sarah Huckabee Sanders's media briefing on Thursday. (Andrew Harrer/Bloomberg News)

White House press secretary Sarah Huckabee Sanders on Thursday called Michael Wolff's “Fire and Fury: Inside the Trump White House” a “book full of lies.” She said during a media briefing it is riddled with “fake stories” and “information that's not true.”

It's merely “some trash that an author that no one had ever heard of until today, or a fired employee, wants to peddle,” Sanders said, referring to Wolff and former White House chief strategist Stephen K. Bannon, who is quoted frequently in the book.

Yet as Sanders dumped on Bannon, she cited Wolff's reporting in “Fire and Fury” as a legitimate source.

“The book also says that he had been sidelined by April [2017], which I think goes further to indicate that he had very little credibility to give much information, particularly after that point,” Sanders said.

So, according to the White House, readers should not believe what is in the book — except this part:

Bannon’s pronouncements about a fifty-year rule for Trumpism might then be supplanted by the rule of Jared, Ivanka, and Goldman Sachs.

By the end of March, this was the side that was winning. Bannon’s efforts to use the epic health care fail as evidence that the establishment was the enemy had hopelessly backfired. Trump saw the health care failure as his own failure, but since he didn’t have failures, it couldn’t be a failure, and would in fact be a success — if not now, soon. So Bannon, a Cassandra on the sidelines, was the problem.

Trump rationalized his early embrace of Bannon by heaping scorn on him — and by denying that he had ever embraced him. If there was anything wrong with his White House, it was Steve Bannon. Maligning Bannon was Trump’s idea of fun.

As The Fix's Aaron Blake wrote Wednesday, savvy readers ought to evaluate the book's claims individually, rather than accept or reject “Fire and Fury” wholesale.

The White House's evaluation process seems to go something like this: If a claim is good for Trump, then it is true; if a claim is bad for Trump, then it is false.

Is it possible Wolff is right about Bannon's influence having waned within the first few months of Trump's presidency but wrong about some other things? Sure. Wolff freely acknowledged in the book he relied on his gut, at times, describing events as he believes they unfolded after receiving conflicting accounts from the aides he interviewed.

But recall that in April, when journalists first reported Bannon and Jared Kushner were clashing and Bannon was being marginalized, White House press secretary Sean Spicer contradicted that narrative.

“He’s very confident in the team that he has,” Spicer said when asked during a briefing whether the president would be “sticking with Steve Bannon.” “They have an unbelievable amount of knowledge, and he believes the counsel that they all bring to the table.”

At the time, it was in the White House's interest to insist Trump was “very confident” in Bannon. Now it is in the White House's interest to say Bannon “had been sidelined.”

Because the White House's position has changed — and appears to be dictated by what is advantageous, rather than what is true — Sanders is not in a strong position to fact-check “Fire and Fury.”