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.
(..) ... in the middle of the desert. Thank you. Alright, come on through. The Senate hearing is expected to get under way in any minute now. Of course the big unknown in all of this is: Will Superman show up? That is what they're really waiting to see. Mr. Keefe. Mr. Keefe. (..)2016 Batman v Superman: Dawn of Justice