A website worth looking at is www.archive.org . It contains digital copies of numerous early Australian books that have been long out of print and extremely expensive to buy second hand.
Just a few are listed below :-
Across Australia, Spencer (1912)The Native Tribes of Central Australia, Spencer and Gillen (1899)
The Northern Tribes of Central Australia, Spencer and Gillen (1904)
The Native Tribes of the Northern Territory of Australia, Spencer (1914)
Horn Scientific Expedition to Central Australia Volumes 1, 3& 4, Horn and Spencer (1894)
Journal of the Horn Scientific Exploring Expedition , Winnecke (1894)
The Native Tribes of South-East Australia, Howitt (1904)
Reports of the Cambridge Anthropological Expedition to Torres Straits Volumes 1-6, Haddon (1901)
Among Cannibals, Lumholtz (1889)
Searchable PDF versions are available for most.