In the Introduction to the practice tests the author writes, "As a writer, my ability to communicate in writing is pretty reasonable (well, my mum thinks so anyway)". Saying something like that, you'd hope she'd know how to use a comma. Sadly, her grammar is so appalling that it makes reading this book distracting at best.
The tests themselves are far too simple, representing the easy end of the spectrum. If you've never done any of these tests before, it might be worth going through them to get a taste for the style. Just don't get this book (as I did) expecting to be able to improve your ability.