Despite Google's often-expressed wish to digitise everything, sometimes you still need to return to the printed word. If you're trying to track down an elusive work, Trove's Australia-wide library catalogue might just be the answer.
Chances are your local library already makes its catalogue available online, so that will be your first port of call (in which case Library Elf might be a useful complementary app).
However, if you need to cast you search further afield, then Trove, powered by the National Library Of Australia, will let you search for books across pretty much every Australian library, and links you to the catalogue listings for those individual libraries. You can search Trove without signing up for an account, but doing so lets you specify your own list of preferred libraries.
Trove's library search capabilities are just a small part of its overall feature set; it also allows searching of older Australian newspapers, and selected web sites, photographs and audio material which has been archived by the NLA. Inexplicably, it's never been mentioned on Lifehacker before, but it's definitely worth adding to your research bookmarks.