Tell-all book by Donald Trump's niece given earlier release date

Early copies of book reportedly contain scathing criticism of US president

US President Donald Trump speaks during  White House's Fourth of July celebrations. Bloomberg

A tell-all book by US President Donald Trump's niece will be published on July 14, two weeks earlier than expected, its publisher Simon & Schuster said on Monday.

The decision comes days after a New York state court lifted a judge's ruling to temporarily blocked publication at the request of Robert Trump, the president's brother.

The court battle is still pending but it is not expected to halt the publication.

An early copy of the book was obtained by The New York Times, which said the book depicted how "a decades-long history of darkness, dysfunction and brutality" turned Mr Trump into "a reckless leader".

The book alleges he paid someone to take a pre-university test for him.

This allowed Mr Trump to attend the University of Pennsylvania’s prestigious Wharton business school, which he has called “the best school in the world".

The book goes through the Trump family history, revealing strong criticisms the family has of the US president.

“He’s a clown,” Mr Trump’s sister, Maryanne Trump Barry, is quoted as saying in the book. “He has no principles. None.”

Mary Trump, a clinical psychologist, writes in the book that her uncle could be a clinical narcissist, The New York Times reports.

“Donald’s pathologies are so complex and his behaviours so often inexplicable that coming up with an accurate and comprehensive diagnosis would require a full battery of psychological and neurophysical tests that he’ll never sit for,” Ms Trump says.

Simon & Schuster said it was advancing the release date of the book due to "high demand and extraordinary interest".

The memoir, titled Too Much and Never Enough: How my Family Created the World's Most Dangerous Man is the best-selling book on Amazon.com, which is accepting early orders for it.

"Mary L Trump shines a bright light on the dark history of their family in order to explain how her uncle became the man who now threatens the world's health, economic security and social fabric," Simon & Schuster said in promotional material for the book.

Robert Trump's lawyer, has said that the legal case against the book is not about freedom of speech but is focused on breach of a 2001 confidentiality agreement.

This marks the second time in the past month that the president has tried to block the publication of an unfavourable book.

On June 20, a federal judge in Washington rejected a White House request to block former national security adviser John Bolton from publishing a memoir critical of the president.