Most of what is written about the Dreamtime is ridiculous.
Stay away from Bruce Chatwin's "The Songlines!"
The best book by far is "Songs, Dreaming, and Ghosts" on The Wangga of North Australia
by Allan Marett, because it has an audio CD with the songs and chants discussed in the book with it. It may be hard to find, but it is new -- 2005. It is also very detailed.

David Turner's book, Life before Eden is also good, but very scholarly as well.

Almost anything by Roland Berndt is worth reading.

yours,

Peter T.