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.
(..) Any sign of antimatter, they'll pick it up. So we still don't know when he's coming? LAIRA: To serve as a Green Lantern means facing the unknown. Although, sometimes facing the familiar can prove to be even more harrowing. Do you sense anything, Laira? Only that the evil still churns and builds. (..)2011 Green Lantern: Emerald Knights