If you live in area where there's no local bookshops around, here are some sites to get bargain books from:
eBay.com.au is where everyone go to for just about anything. Local pick-up purchases may be cheaper. Some offer free postage or minimum fees. Some combine shipping.
Amazon.com.au is a great place to score ebook bargains. There's not a lot of printed books at bargain prices.
Bookdespository.com offers free delivery worldwide. Amazon acquired this company in 2011. The site says that books are shipped either from UK or from Australia. Grab bargain printed books. They hold promotional discounts all the time. Nope, they don't sell ebooks.
Fishpond.com.au offers free delivery to Australia and New Zealand. Get book bargains and other items on promotional sale. They don't stock items themselves so expect delivery to take longer than usual. They have sellers all over the globe listing products for sale. You can list your items as well. For shipments to Asia, US/Canada, South Africa, and UK/Western Europe, there is a basic fee plus additional charge per item.
Wordery.com offers free delivery worldwide. They have ready-to-ship book promotions from time to time. You get a discount if you buy 2 of those. These are ready to ship from their UK warehouse.
Booktopia.com.au is an Australian local, online bookstore. It also sells eBooks, DVDs, Magazines, and other items. It charges a flat rate of A$6.95 for shipment to Australia and New Zealand. Seasonal free shipping offers happens. Purchases A$80 and above require signature on delivery.
Worldofbooks.com offers free delivery in Australia and worldwide. Score used book bargains on the site.
Mightyape.com.au offers delivery to Australia for A$6 per shipmentvia Auspost eParcel. Delivery to New Zealand is at $4 per shipment. International shipment is also available. Mightyape is based in New Zealand and sells book bargains and more.
Angusrobertson.com.au offers delivery within Australia at A$7.5 per order. There is no international shipping available. The Sydney based warehouse sells books Australia wide.
Catchdeals.com.au lists bargains all the time. Score book bargains and more. Some items include free shipping. Check for the free shipping icon as you browse.