I reckon it's a pretty useful guide. I've found that it's a pretty good guide to supplement my teacher's explanations and comments on my essays.
Basically, the book tells you the exam format and a preparing for the essay. Then it has four sections:
1. Spoken language
2. Written language
3. How to write an English Language essay
4. Exam success
For the first 2 sections, it's got sample extracts and questions that you can answer to prepare you for the exam.
In the third section, it gives you a few notes on Australian English, attitudes to varieties, functions of language, etc. It also teaches you how to analyse the essay question and how to plan afterwards. The best bits are that this section gives you 14 sample essays which the authors deem to be of A+ standard and they also give you some essay topics to polish your essay writing skills to prepare you for the exam.
Section 4 is pretty much self-explanatory - it gives you hints on the three sections in the exam as well as exam hints.
I hope that brief summary of the book is enough for you to know the structure and content of the book.