Why another market? Why people don't use gumtree/ebay or whatever forum to sell their used books?
Compare to cars/houses, books are quite simple - the only practical searchable attribute is the book name. Thus no point to dedicate a website just for the book.
I would suggest u guys change strategy to build a book-trade website, for example, I can give my used books to you, and you would owe me 1 book-point, then I can use the book-point to purchase used books from someone else.
And for books, a community is more important than marketplace, probably you should add more web-2.0 elements into it.
Also, I personally don't understand why so many australian websites put geotrust logo at the footer - it is tooooo ugly.