Valore is REALLLY slow. Their whole business focuses on textbooks/university students, so if you don't have inventory that's appropriate there, it's probably not worth your time. Since they're a textbook site, the sales are very seasonal - basically August, January, and a little in the spring for summer sessions.
 
It is free to list there, so that's good - but don't expect any major shift in your sales by adding them.