The five most common bird guides are outlined on this web page: https://bestbirdphotos.com.au/best-5-australian-bird-field-guides/
I agree that the Australian Bird Guide is generally considered to be the gold standard, although there is nothing particularly wrong with any of the others. I use the ABG for general work but it is not particularly portable. Morcombe used to have a pocket sized guide which serves well for basic identification in the field; I bought mine several years ago, and I am not sure if it is still printed. It lives permanently in the glove box of the car!
There are also phone apps available which include bird calls, often useful in identification if you have a good ear for that sort of thing. I don't use Australian apps but I use apps in other countries, with the Audubon iPad app particularly useful in the US. Note that we don't support call playback to attract birds.
No book is perfect so it often pays to have more than one available. They differ in purpose and style, as well as organisation of material, indexing etc. Some maps of distribution are better than others. In particular, some people prefer the illustrations in one book over the other. It is generally better (in my view) to use books with drawn images rather than photographs, as photos can be deceptive in terms of presenting details and colours, if not very carefully prepared and edited for the purposes of identification (rather than just the art of photography). Skilled artists can better illustrate key identification features. Apps may use photographs and often include multiple photos to try and show different features (which is not really possible in field guides to keep the size of the book in control).
Always try and get the latest version in print. Later versions (a) correct mistakes in text and drawings, (b) can provide updated species lists and names (these change from time to time for example the 'Rainbow Lorikeet' and 'Crimson Rosella' have become subdivided as researchers get better information on things like genetics), and (c) can have updated rare vagrant records.
Simon