I used this for my law exam at University, which was open book, and found the index very hard to use, as did my friends. If you want to use this book you are best spending a lot of time reading through it and putting your own sticky notes in to show where things are, because using the index you will never find it. therefore not good as a quick reference book.
on the other hand if you are willing to spend hours reading it, it is very detailed and informative and summarises the important key parts of an Act quite well. so is still useful, depending on your time.
The only other negative point is that it can be quite jumpy, with Acts talked about at several points in the book. Would have been more useful to have everything from that Act in one place.