It was written by Mary Jordan, a Pulitzer Prize winning reporter at the Washington Post.
Trump was inaugurated as President on January 20 2017, but Melania and the couple’s son Barron didn’t move into the White House until June.
Instead they continued living in New York’s Trump Tower.
At the time it was said this was to allow Barron to finish his school year without interruption.
However according to Ms Jordan’s explosive book Melania was in fact using the time to renegotiate her prenuptial agreement with her husband.
The first lady allegedly wanted to make sure Barron would be treated the same as Trump’s children from previous marriages, Donald Jr, Ivanka and Eric, when it comes to inheritance.
Ms Jordan attributes the claim to three people who are close to the US President.
She adds Melania’s bargaining power was boosted by being married to Trump for longer than any of his previous wives, at 15 years.
READ MORE: Melania Trump – Why she is ‘comfort blanket’ for Ivanka Trump
The book is based on more than 100 interviews including with Melania’s Slovenian classmates and society associates in New York.
Roger Stone, a lobbyist who worked on the Trump campaign, told the author Melania played a key role in persuading her husband to run for the presidency.
Referring to the first couple Ms Jordan wrote: “They are both fighters and survivors and prize loyalty over almost all else.
“Neither the very public Trump nor the very private Melania has many close friends.
“Their loner instincts filter into their own marriage.”
According to Ms Jordan Melania also played a pivotal role in persuading Trump to adopt Mike Pence as his running mate in 2016.
The author stated: “She believed that he would be content in a number two spot and not gun for the top job.”
Melania was born as Melanija Knavs in Novo Mesto, then Yugoslavia and now Slovenia, in 1970.
She worked as a model, in which capacity she moved to New York City in 1996.
In 2005 she married Donald Trump and a year later obtained full US citizenship.
She is only the second foreign born women to be first lady of the United States, after the British born Louisa Adams who was married to John Quincy Adams.