Build your German language skills by mastering pronouns and prepositions in no time at all! Practice Makes German Pronouns and Prepositions gives you a quick, painless way to master two essential building blocks of German language fluency. Using numerous everyday examples, it demystifies German pronouns and prepositions and provides dozens of skill-building exercises in a variety of formats, including fill-in-the-blanks, sentence rewrites, and translations.
I feel like I know German better than this guy with all the typos and his sometimes scattered way of teaching the language. I don't recommended any of his workbooks, because they fail to help you bring all of your knowledge together in a concise manner so that you can easily understand what you're learning.
A while back someone wrote a book with the title, "Don't sweat the small Stuff," and ever since then, the phrase has entered our lexicon. And it's true to an extent, that you don't want to get bent out of shape about little details. But after you've learned a language, if you want to go from speaking well to speaking as well as a native speaker, you are going to have to try to fine-tune your already developed skills. You're going to have to improve what the Germans call "Kleinigkeiten."
I've completed a ton of the "Practice Makes Perfect" books, and not a one wasn't worth the price, but "German Pronouns and Prepositions" has perhaps improved me the most. It contains exercises on grammatical concepts that not only have to be learned once, but have to be continuously practiced in order for one to maintain their skill. After a certain threshold, you don't really get better at grammar. You just "lose it" if you don't "use it."
My advice, if you already speak and write German, is to use this book. And then, after you complete the exercises, keep it handy for when you need the appendices to check out some little "Kleinigkeit" about a reflexive pronoun in the dative case (or whatever your personal grammatical bugbear might be). Highest recommendation.