This article below comes from Bubblecow and makes interesting reading for new writers and those seeking a contract with a publisher.
"We live in a world dominated by best sellers. A new writer can be forgiven for thinking that the mega-success of writers such as Dan Brown, J. K. Rowling and Stephen King represent to norm. The reality is very different, with debut novelists struggling to even get reviews, never mind selling millions of copies.
So, how many books can a new non-best selling novelist really expect to sell?"
Click here to read the full article: How Many Copies Do Novels Sell?: