Quick question, did you actually mean, «1 book in 5 doesn't earn back its advance» Or did you mean 4 books in 5 don't earn out its advance. (thecreativepenn.com)
A lot of books never earn out their advance. (jimchines.com)
It doesn't seem to matter that the previous books earned out their advances or that the fans are asking the author for the next book. (makingitupasigo.com)