Former president Fidel Castro will be the subject of a new volume of memoirs about his life as a Cuban revolutionary, the country's larger-than-life leader and a longtime nemesis of the United States.

In the twilight of his life, the latest tome about Castro will be written by Katiuska Blanco, a former reporter with official newspaper Granma who penned two earlier books about the 86-year-old.

Castro's much documented life has been the subject of several books, perhaps most famously one written a quarter-century ago by his close friend, Nobel Prize-winning Colombian writer Gabriel Garcia Marquez.

Blanco, 48, his newest biographer, is also the self-described "polisher" of Castro's own writings.

She has been a perennial collaborator with Castro on various writing projects, as the author of two biographical books about him and his family, one written in 2003 and the other in 2008.

She also collaborated with Castro on an account he wrote in 2010 about his efforts to overthrow dictator Fulgencio Batista, and his autobiography that appeared in 2012.

Blanco, who had access to Castro's archives for the book, insisted that the work was not an "official" biography, telling AFP that "nobody tells me what to write."

As Blanco put Castro's thoughts to the page, Fidel meticulously "annotates, highlights, amends, extends," she said.

Blanco said Castro has been an avid user of the Internet, which he has used with gusto since May 2001, but he jots down many of his thoughts by hand.

He "never writes or does anything without giving it all of his passion, his interest and the force of his entire spirit," Blanco said.