thanks 
do the libraries have a lot of copies?
I find that generally the library will stock a few copies of prescribed textbooks, but usually, the current edition of the required text is restricted to two-hour or overnight loans. You can probably get away with borrowing an older edition, which is usually pretty much the same and often available as an 1-week loan, which can be renewed multiple times (up to 10 I think).
PROTIP: Get a CAVAL card (just ask at the desk at any unimelb library), which will allow you to borrow books from any university (including Monash and Deakin, for example). Often the textbook which is prescribed at Unimelb is available at another uni, but is not a prescribed text there. So, they will often be in short supply due to low demand, but also allow longer borrowing periods for a current edition text (not restricted to overnight), for the same reason.
Furthermore, if you borrow at Monash Uni, your books will be automatically renewed, until you are not allowed to keep renewing (10 times is the max), which means you effectively have an 11-week loan and you don't have to worry about constantly renewing your books every week. This is much better than at Unimelb, where forgetting to renew your books on time even once means you have to return your books (you can't renew it again) and face a fine.