Six Practice Makes Perfect Books in One: Complete German Grammar; German Verb Tenses; German Pronouns and Prepositions; Intermediate German Grammar; German Conversation; German Sentence Builder
For anyone wondering if this book is worth it: Go get yourself a proper German grammar book like Grammatik Aktiv and supplement it with a decent vocabulary book, such as those short-story books.
This book has some good exercises; however, after a while, it becomes very difficult to maintain your momentum.