"It's the greatest business book of all time", Trump said, according to Manigault Newman's book.
Manigault Newman also alleges that Trump allies tried to buy her silence after she left the White House, offering her $US15,000 ($A20,540) a month to serve in a "senior position" on his 2020 re-election campaign along with a stringent nondisclosure agreement.
She has since referred to the administration as a "plantation", claimed she was ostracized for being black, and vowed she would never again vote for Trump. "I'm sure Kat will fill you in on that convo if you ask her nicely".
During a White House pool spray, Trump responded to a shouted question about Manigault and her book- which claims that there are tapes of Trump using the N-word - by calling her a "lowlife". "Just think how many copies I'd sell - maybe a commemorative inauguration copy?"
Manigault Newman, 44, met Trump in 2004 when she was a candidate on the American version of The Apprentice, which he hosted.
In the book, Manigault Newman painted the president as scattered, self-absorbed, misogynistic and insecure.
She said: 'I was told exactly what Donald Trump said - yes, the N-word and others in a classic Trump-goes-nuclear rant - and when he's said them.
'During production he was miked, and there is definitely an audio track. She says that Trump used racial slurs like the "N-word" during tapings of his reality show The Apprentice and that there are tapes of him saying it.
As reports of accounts inside the book leaked out, White House Press Secretary Sarah Sanders slammed Manigault Newman as a "disgruntled former White House staffer" whose book is "riddled with lies and false accusations".