I bought just a workbook because i wanted to practice more. I have a couple of different grammar books, plus i go to websites for more resource. I've gone though a few chapters and i have already found differences in what I've learned till now and in what this book suggests. But even my online recourses say grammar in this book is wrong. So this left me a bit perplexed and if i find more mistakes like these i'm gonna regret buying this book, even though there are only few. Otherwise i like the structure of it. The excercises are very much my way of learning. They are to the point, easy to check with the key in the end. Don't buy the workbook on it's own if you don't have any kind of guide. But the book could be a bit more thicker for this kind of price.