Bob Taits books are not worth the paper they are written on, is my personal opinion. Anyone that suggests they are good has not had to use their knowledge in an aviation environment. Yeah, the questions are like the real ones and if you memorise the answers you will pass the CASA exam, but there is so much more to it then that. Bob Tait has dumbed down the theory and uses terms to make it simple and easy to read. He has written the books to cover the bare minimum sections of the syllabus. The number of pilots that now don't know the basic aerodynamic definitions is amazing. His BAK book leaves so much out, it doesn’t even introduce the different loading charts and his air law chapter must assume that all students have a VFG as it is also very light on for content.
Spend the money and get the Trevor Thom (Aviation Theory Centre) books. They are more in depth, harder to read and don't have as many questions, but at the end of the day you will pass the exams because you know your stuff, not because you have memorized the answers.
If you can find a copy of Dyson Van Hollands books they are gold! But have been out of print for a while now I think.