Anderson, who is known for playing the character of special agent Dana Scully on popular American TV series 'X-Men', said she is enjoying writing the book alongwith Rovin, reported Entertainment Weekly.
The book is titled 'EarthEnd Saga'.
Ryan, 62, has penned several books and biographies including those on Sylvester Stallone, Elvis Presley and others.
"I enjoy writing, but don't usually allow myself the time, and I don't think I'd ever think to write something in this genre without the prodding of someone like Jeff," the 45-year-old actress said.