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.
(..) We found dollars, lira, a lot of gold and golden wedding rings. Understand? And what happened to the second one? I don't know. He fled to the mountains. His fate is unknown. Is that all? Yes. Oh, remembered. The man who had escaped... We learned about this later. He was a doctor. (..)1981 To Kill a Cop