Fire and Fury, a blistering account of Trump's first year as president, has sold four million copies worldwide since it came out. Communications director Leigh Altshuler of Manhattan's the Strand bookstore said that the book sold out immediately and took days to restock.

"There was a snowstorm the day [Fire and Fury] got delivered. Everyone was coming in all day long," Altshuler said. "The copies couldn't make it from the hand truck to the tables because people were taking it out of the booksellers' hands."

This time around, with Wolff's sequel Siege: Trump Under Fire hitting stores on June 4, Altshuler said she does not expect the same kind of frenzy and that there is "significantly less demand" for the book. She attributed the lack of interest to the saturation of political books in the market and a lack of trust regarding Wolff's credibility. Readers are looking to other sources for more reliable information, Altshuler said. And in the months since Fire and Fury hit stands, they've had no shortage of books pulling back the curtain on the 45th president's chaotic management style -- the likes of Bob Woodward's Fear: Trump in the White House, Cliff Sims' Team of Vipers, and Vicky Ward's Kushner Inc. have all offered up headline-making looks at all things "The Donald".

With this kind of saturation, Wolff has had to scramble to offer up his own blockbuster scoops and there's evidence to suggest his claims may have exceeded the facts at hand. Siege chronicles Russian meddling in the 2016 election, the Brett Kavanaugh hearing, and asserts that Mueller drafted an indictment of the President. The Justice Department has already denied the existence of documents including the indictment itself even before the book's release. Unless the author comes forward with reliable sources or the documents to support his research, this lack of validity may hurt sales.

Wolff has been slow to respond to questions of plausibility, but is now starting to make public appearances. In recent interviews including one with Steve Inskeep of NPR on Sunday's Morning Edition, Wolff vaguely defended his findings saying that he trusts his own reporting and sources even though many are unnamed. According to ABC publicist Lauri Hogan, Wolff was set to appear on [US] ABC's The View on Monday, but was taken off the scheduling. The View declined further request for comment. In terms of the future of his book tour, if he brings forth concrete research and documents that prove his claims, Dan Kennedy, associate professor of journalism at Northeastern University and regular panelist on WGBH's Beat the Press, said that some of the critiques will dissipate and the book will gain traction.

"If [Wolff] can verify that fact, it's going to have to be better than saying 'unnamed sources described the documents to me.' But if he can verify that to most people's satisfaction, then yeah, some of the sniping will go away and people will take this book more seriously," Kennedy said.

Another setback that may diminish sales, Kennedy said, is that Wolff's key source and ex-White House chief strategist Steve Bannon lost his job and, thus, his West Wing access. That's made it more difficult for Wolff to get a privileged peek into the Oval Office doings.

"My guess, and this is just a guess, is that the new book will not sell nearly as well as his first book because when he was channeling Bannon the first time, Bannon was in the White House and wielding quite a bit of power," Kennedy said. "This time, Bannon is on the outside looking in, and I don't think that what Bannon has to say is going to be nearly as interesting as it was the first time around."

According to Altshuler, Fire and Fury sold so many pre-sales that Henry Holt and Co. released the book four days ahead of schedule. Siege: Trump Under Fire can't even hold a position on Amazon's best seller list. Wolff's sequel went from the 59th position to dropping off the list entirely on May 31. However, the book holds #1 in hardcover and #2 on the kindle edition on Amazon's new release list as of June 3.

Although Michael Wolff's latest may not do as well as Fire and Fury, political books are still of interest to the public. In comparison to a stellar year in the sale of political-related books in 2018 with a 44 per cent increase in sales according to The NDP Group, the same topic has seen a decrease of 37 per cent in 2019.

Executive Director of Business Development at NDP Kristen McLean said that 2018 was the "biggest year" for political books since the company started tracking the topic's sales in 2004. So far, McLean said that 2019 has generally been weaker in the category, however, nonfiction sales are still strong. The biggest political book so far this year is a printed version of The Mueller Report.

"Political books had their best year growth ever in 2018," McLean said. "Compared to that, which included the release of the early books in 2018, we are down in the political books category this year and that even includes the release of the Mueller report.

"But, in general, the climate for political books is still very strong. The climate for adult nonfiction overall is still very strong. So, we're expecting good numbers on the book, but I can't give specific prediction of whether or not it will exceed the previous or come even close [to Fire and Fury] because that was quite a break-out."

Michael Wolff did not respond to a request for comment for this story.