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.
(..) Extremely dangerous. Extremely dangerous. Kill on sight. Kill on sight. Kill on sight. Night Fury. Speed unknown. Size unknown. The unholy offspring of lightning and death itself. Never engage this dragon. Your only chance: Hide and pray it does not find you. (..)2010 How to Train Your Dragon