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.
(..) But the last thing he expected was... Lightning McQueen! You know, I don't think anybody expected this. The rookie sensation came into the season unknown. But everyone knows him now. Will he be the first rookie to win a Piston Cup and land Dinoco? The legend, the runner-up, and the rookie! (..)2006 Cars