This book really is a useful addition to Teach Yourself Dutch. It goes into most of the grammar points in TYD in more detail, so that if you were not so sure about something in TYD then this book includes more detail, examples and what is really useful are the many exercises to make sure you grasp the points correctly. It is also worth buying because it includes 'extras' about speech such as style, including strong language, interjections and differences between informal and formal. Obviously these are extremely helpful if you want to sound more native.