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.
(..) Dialogue: Marked=..,Default,NTP,!Effect,The only problem is, l can't remember\Nwhat l've forgotten. Dialogue: Marked=..,Default,NTP,!Effect,Hey Ron! Somebody broke into Gringotts.\NListen. Dialogue: Marked=..,Default,NTP,!Effect,''Believed to be the work\Nof Dark wizards or witches unknown... (..)2001 Harry Potter and the Sorcerer's Stone