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.
(..) A dark, very pretty girl. - Ling or... Long. Something like that. - Who else? I'd never heard of them before. It was a very inexpensive second feature, with unknown... And you weren't under an emotional stress, were you? No. I wasn't. - I think the point is made. (..)1957 12 Angry Men