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.
(..) She's programmed to do that should certain conditions arise. They have. - Like what? - It seems she has... intercepted a transmission of unknown origin. - She got us up to check it out. - A transmission? Out here? - Yeah. - What kind of a transmission? Acoustical beacon. It repeats at intervals of seconds. - S.O.S? - I don't know. Human? - Unknown. - Well, so what? Well, we are obligated under section eight... I hate to bring this up, but, uh... (..)1979 Alien