If you've never been published before, you're an 'unknown quantity', so you're going to have difficulty selling your first novel.
('chiefly US') The 'big unknown' [=the important thing that everyone would like to know] is how investors will react.
A 'fear of the unknown' kept her from changing jobs.
(..) my runnin' days was over. So I went home to Alabama. Moments ago, at . p.m., as President Reagan was leaving the... ...five or six gunshots were fired by an unknown would-be assassin. The President was shot in the chest... I picked up the mail. And one day, out of the blue clear (..)1994 Forrest Gump