I was required to by this workbook for my spanish conversation class. It's an upper division college level class, and I was really disappointed when I started working in this book. The first chapter and 15+ pages was all about the usage of Direct and Indirect Personal Pronouns. For me, this is useless busy work.
If you are a newcomer to the idiosyncrasies of spanish grammar, then this book would be extremely helpful. It includes explanations about the grammar that are followed by questions to answer. I've only completed the first two chapters so far, and I hope it gets more difficult. Yet, for advanced students, there is no point to purchasing this workbook.