Los Angeles - Prince was writing a memoir titled The Beautiful Ones shortly before his death.
The Purple Rain hitmaker's body was reportedly discovered at his Paisley Park compound in Minnesota early Thursday morning, sources confirmed to website TMZ.
Authorities were called to a medical emergency at the estate at around 09:43 but did not immediately identify that the body was that of the 57-year-old singer.
His publicist, Yvette Noel-Schure, confirmed the news to The Associated Press.
The Purple Rain hitmaker announced the news of his book at a concert at the club Avenue in New York last month.
He told the crowd: "The good people of Random House have made me an offer I can't refuse!
"It's going to be called The Beautiful Ones. I literally just got off the plane. I'm going to go home and change and put some dancing clothes on. Props to my brother Harry Belafonte."
The book was expected to be released by publishers Random House in Autumn next year.
The 57-year-old singer enlisted the help of critic Dan Piepenbring who writes for the Paris Review to help pen the tell-all piece.
In a bid to get a reaction from the crowd, he asked: "You all still read books, right? My brother Dan - Dan Piepenbring of the Paris Review - is helping with it. He's a good critic. That's what I need. Not a yes man."
After he'd made the big reveal, he told the club full of people he was off home to get into his dancing clothes and he'd return ready to dance with everyone.
He said: "If you don't mind, I'm going to go home and change real quick and come back and dance with y'all"