Talking to a few Poms recently quite a lot of people are complaining about how expensive books are here... I use Bookdepository.co.uk which has as big a selection as Amazon with good discounts on all books PLUS FREE DELIVERY TO AUSTRALIA. I have been using them back in the UK for >5 years and never had any probs. I also like the fact that they send out the books in stock immediately (ie not delaying the whole parcel if say one of the books wasnt in stock), and I usually get the books 3-4 days after ordering.
Just wanted to share this in case like me anyone out there has a serious book habit to support!! :p