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.
(..) And since so neighboured to his youth and humour... To draw him on to pleasures and to glean whether aught to us unknown afflicts him thus... ...that disclosed, lies within our remedy - He hath of late much talked of you, good sirs And sure I am, two men there are not living to whom he more adheres (..)2015 Hamlet