In the book, Stewart shares her personal diaries of her last three years by Farrah's side. Fawcett lost her battle with cancer on June 25th.
According to Stewart, the book has the support of Ryan O'Neal, Fawcett's longtime boyfriend. Stewart also says Farrah encouraged her to write the book.
A portion of the proceeds from the book will go to the Farrah Fawcett Foundation to support cancer research, the publisher said.
Stewart also worked on the NBC documentary, "Farrah's Story," as a videographer and producer.