Donald Trump’s niece, his deceased brother’s daughter, is set to publish a tell-all book this summer that will detail “harrowing and salacious” stories about the president, according to people with knowledge of the project.

Mary Trump, 55, the daughter of Fred Trump Jr. and eldest grandchild of Fred Trump Sr., is scheduled to release Too Much And Never Enough on July 28, Simon & Schuster confirmed Monday, just weeks before the Republican National Convention.

One of the most explosive revelations Mary will detail in the book, according to people familiar with the matter, is how she played a critical role helping The New York Times print startling revelations about Trump’s taxes, including how he was involved in “fraudulent” tax schemes and had received more than $400 million in today’s dollars from his father’s real estate empire.

As she is set to outline in her book, Mary was a primary source for the paper's Pulitzer Prize-winning investigation, supplying Fred Trump Sr.’s tax returns and other highly confidential family financial documentation to the paper. 

Details of the book are being closely guarded by its publisher, Simon & Schuster, but The Daily Beast has learned that Mary plans to include conversations with Trump’s sister, retired federal judge Maryanne Trump Barry, that contain intimate and damning thoughts about her brother, according to people with knowledge of the matter. 

Mary Trump has kept out of the public eye and has not spoken publicly in decades—but in 2000, amidst a bitter family court battle over Fred Trump Sr.’s will, she told the New York Daily News, "Given this family, it would be utterly naive to say it has nothing to do with money. But for both me and my brother, it has much more to do with that our father [Fred Jr.] be recognized," she said.

Fred Trump Jr., the firstborn son and once the heir apparent to his father’s real estate empire, worked for Trans World Airlines after turning his back on the family business.

He died in 1981 aged just 42 from a heart attack owing to complications from his alcoholism, leaving behind a son, Fred the 3rd, and daughter Mary, who has a Ph.D. in clinical psychology.

The circumstances of Fred Trump Jr.’s descent into alcoholism are also aired in the book, with allegations that Donald and Fred Trump Sr. contributed to his death and neglected him at critical stages of his addiction.

In a 2019 interview, Donald Trump admitted to pressuring his brother over his career choices but said he had come to regret it. “I do regret having put pressure on him,” Trump told The Washington Post. Discussing his brother and the family business Trump said it “was just something he was never going to want” to do. 

“It was just not his thing...  I think the mistake that we made was we assumed that everybody would like it. That would be the biggest mistake... There was sort of a double pressure put on him,” Trump admitted.

After Fred Jr.’s children brought their messy court case against the family—contesting their grandfather’s will and alleging it was “procured by fraud and undue influence” on the part of Donald and his siblings—they highlighted Donald’s callous treatment of family members as he, along with siblings Maryanne and Robert, cut off the medical benefits to his nephew’s sick child William, who was born with cerebral palsy. The move, the family said at the time, was payback for Mary and Fred the 3rd’s challenge to the will.

That court case produced a treasure trove of confidential and highly sensitive Trump family financial documents, including Fred Trump Sr.’s tax returns, which almost two decades later would fall into the hands of The New York Times and form the basis for one of the most stunning pieces of journalism in recent years. 

In June of 2019, The Daily Beast reported how The New York Times Trump tax team imploded when four-time Pulitzer Prize-winner David Barstow went rogue, aggressively pursuing a source of their groundbreaking investigation to ghostwrite a book and secure a six-figure payday—a move explicitly forbidden by the Times’ ethics rules.  

That story detailed how Barstow went behind his colleagues’ backs and pursued the source—who was not his source to begin with—even after his editors told him not to do the book. 

Barstow even went so far as to make a surprise visit to the source’s residence after they ceased communications with him, staying at least three hours, and ringing the front and back doorbells multiple times as the person hid in their home.

“The source was freaked out. The source felt invaded. They ended up hiding until he left the residence,” a person with knowledge of the situation told The Daily Beast at the time, adding that the source considered calling the police. 

While Times Executive Editor Dean Baquet backed Barstow over his questionable ethical decisions and Barstow claimed he acted appropriately, he soon left the paper to take up a position leading the University of California Berkeley Graduate School of Journalism’s investigative reporting program. 

At the time of publication, The Daily Beast did not name the source and took extensive measures to protect their identity. In the upcoming book, however, Mary Trump will out herself as a source for the Times and detail her involvement working with journalists Russ Buettner, Susanne Craig, and Barstow to crack the story, according to people with knowledge of the matter. 

The book is sure to send shock waves through Washington and the Trump family just months before the election and it comes hot on the heels of John Bolton’s much-anticipated memoir. But unlike all the books by former Trump staffers, this is the first time a Trump family member has written a tell-all that is highly critical of the president.

The bad blood between President Trump and his niece dates back 20 years to the fight over Fred Trump Sr.’s will and the actions he took to cut off financial and medical support for her brother’s ill child. Now that feud is about to spill out into the public eye during a critical election year, with the president struggling to shore up his plummeting popularity.

“My aunt and uncles should be ashamed of themselves,” Mary Trump said about Donald Trump and his siblings in that rare 2000 interview, which provides a preview of the tone of her book. “I'm sure they are not.”