When I was in graduate school my professor was fond of saying, "If you use Rosetta Stone to learn a foreign language, and you do so for something like six hours a day, you're really going to know how to ask someone where the bathroom is, like no one's business." His point was that there is a difference between learning the rudiments of a language, how to navigate very basic conversations involving things like "Where is the ...." or "How much is the ..." versus expressing one's own ideas, using concrete language to get across something abstract.
"German Sentence Builder" does a mighty fine job of helping one transition from parrot to songbird. All of the books I've used in the "Practice Makes Perfect" series have ranged from the helpful to the wonderful, and this book of exercises and refreshers should probably be put in the latter category. It's one of the best in the series that I've encountered thus far, if not the beau ideal.
There are multiple choice exercises inside, but there are also much more open-ended assignments that allow one to get beyond asking and answering question, down to the nitty-gritty of composition.
The best way to become a proficient German writer is not that much different from the path that a native English monoglot with the same desire would use to become a better writer in their own language. Read articles, and then later book-length works in the foreign language (I've found that reading and translating poetry also helps strengthen one's intellectual muscles, but that might just be me), and then try your own hand at the various forms. But in the sequence of crawl-walk-run, reading a book or writing an article in one's second language is very much in the "Run" category. "German Sentence Builder" can take you from walking to a light jog (to hyper-extend my metaphor) providing you take it seriously and work your way through it with some regularity.
And if you want to get to the point where you can write a book or dissertation in German It can be done. Joseph Conrad, for instance (whose first language was Polish) wrote one of the modern English-language masterpieces of all-time, "Heart of Darkness", but if something more ambitious than penning a letter without making a faux pas is your goal, you're going to have to treat "German Sentence Builder" as a stop-gap on a much longer journey (get ready to run a marathon, have plenty of anti-chafing tape on hand, and remember to hydrate).
In any event, highest recommendation for intermediate and advanced German speakers.