When you start reading the book and do the tests, be careful, because the book contains number of mistakes. I found it extremely irritable because it destructs you from your main goal of practising. DO not bother timing yourself, because you will more than like discover that many of the practical exercises to not make sense. Why? Simply because the author made a mistake or left a digit out. Then when if you decide to check your answer with the answers given in the book, you will first have to find that answer, simply because the author decided that they don't have to be in any particular order or, indeed, numbered correctly!
Overall, the book is a big disappointment and not worth it...