Book after book, story after story, news cycle after news cycle all come back to the same uncomfortable question: Is President Trump fit for office?

You can expect to hear the question asked a lot more in the coming weeks.

Bob Woodward's forthcoming book "Fear: Trump In the White House" includes a wealth of new evidence that is making Trump's fitness a subject of discussion again. Furthermore, the book indicates that it already is being discussed by some of the highest-ranking officials in his administration.

According to the book, which is largely based on confidential sources, some of the president's top advisers view him as a danger to national security. Woodward quotes defense secretary James Mattis saying -- to people described as "close associates" -- that Trump had the understanding of a "fifth or sixth grader."

Woodward quotes others describing Trump as "unhinged" and an "idiot" and a "liar." He has chief of staff John Kelly saying "we're in crazytown." And so on and so on.

"Fear" doesn't actually come out for another week, but the Washington Post, where Woodward has worked for decades, obtained a copy and published excerpts from it on Tuesday. So did CNN. Other news outlets are likely to publish additional material from the book in the coming days, keeping "Fear" in the headlines straight through its September 11 release date.

Even before the excerpts came out, "Fear" was getting attention. When it was announced in late July, the title hit No. 1 on Amazon's best sellers list thanks to a spike in pre-orders.

On Tuesday morning, "Fear" was holding steady at No. 12, an enviable spot one week before launch day. After the excerpts came out, it soared back to No. 1.

Trump responded to the reporting by saying that Woodward might have made the stories up, contradicting his own previous praise of Woodward's reputation.

"It's just another bad book," Trump told The Daily Caller.

He was right in one respect: "Fear" is not the first book to contain damning claims about the Trump White House.

That's the thing: There's been a succession of these reports, almost ever since inauguration day, depicting the White House as dysfunctional and the president as, in his own chief of staff's words, "unhinged."

Newspapers like The New York Times and networks like CNN have led the way with scoop after scoop about Trump's behavior behind closed doors.

Then came books, most notably Michael Wolff's "Fire and Fury," which portrayed the president as grossly unfit for office.

On "CNN Tonight" last January, Wolff said it would be "irresponsible not to" question Trump's fitness.

"Fire and Fury" helped bring fears about Trump's competency and stability to the forefront.

Even before the book came out, polling indicated that many Americans believed Trump is not fit for office. But others saw this issue as an invention by anti-Trump members of the media.

During the launch of "Fire and Fury," Wolff's credibility was repeatedly called into question. Critics pointed to mistakes in the book and cast doubt on his sources and methods.

Credibility was also an issue when former Trump White House aide Omarosa Manigault Newman released her tell-all, "Unhinged," last month.

She, too, questioned Trump's fitness for office and described him as mentally waning.

Some details in her book were backed up by audio recordings, but her convoluted reality TV history with Trump and some basic errors in the text were cited as weaknesses.

Woodward is different.

As the CNN team of reporters who read "Fear" in advance wrote on Tuesday, "his reporting comes with the credibility of a long and storied history that separates this book from previous efforts on Trump."

Woodward is one of the most distinguished and best known journalists in America. He has authored or co-authored 18 books.

For that reason, among others, "Fear" will receive widespread attention in the weeks ahead.

No doubt, some will shrug. When Tuesday's excerpts were published, the reactions from Trump's loudest detractors on Twitter could be summed up in a single word: Duh. And from his biggest fans, a different word: Fake.

But beyond those predictable responses, there are important reporting insights contained in the book. Much of it comes back to the fundamental question about fitness.

"Woodward's new book seems to confirm what many people still are not willing to acknowledge: the president is not mentally fit," Mother Jones D.C. bureau chief David Corn wrote on Twitter Tuesday afternoon.

Corn, a vocal critic of Trump, co-authored the best selling book "Russian Roulette" earlier this year.

Another journalist who has been outspoken about Trump, Vox's Ezra Klein, tweeted on Tuesday that "there should be a word for the pain of being repeatedly confronted with what you already know is true."

"That's the experience of reporting on Trump, and reading these Trump books," Klein said. "What's going on in the White House is exactly what it looks like, and that's scary every single time."

In interviews, Woodward will likely be asked about this. His first TV interview about "Fear" is scheduled to air on "CBS Sunday Morning" this weekend, according to two sources with knowledge of the matter.

Then he'll appear on a variety of television networks and other outlets. His publisher, Simon & Schuster, is confident that "Fear" will be a No. 1 best seller, one of the sources said.