50 bucks is a hefty price to pay for a workbook so the main question is this book worth it and will it improve your Russian improve. Well the answer is yes and here's why--
I own pretty much all of the highly praised Russian material including Using Russian a Guide to Contemporary Usage, Using Russian Vocabulary, and Modern Russian An Advanced Grammar Course. None of these surprisingly have a workbook. I cannot say that's a bad thing, but to have the ability to reinforce concepts, practice what you learn, build vocabulary, and be introduced to more examples is a serious benefit. This workbook corresponds beautifully with Wade's grammar book. I found myself seamlessly going back and forth between the two, and the exercises correspond well with what you learn in each topic. But here's the kicker and ultimately why you should shell out 50 bucks-- Answers are provided! This adds a high amount of practical value and you can easily check your work for each exercise. With some hard work, one can gain a ridiculous amount from this. This brings up my next point -- this isn't really for beginners. One should have at least completed their first year of Russian. I'm on my 3rd year of Russian and I had to look up words and was challenged by some complex sentences structures. You should at least have a firm grasp on basic Russian grammar like case endings, case usage, verbs of motion etc... as well as a good vocabulary. If you're lacking in the areas it is of course still possible but will require some extra effort.
It can be used as an independent resource but of course this is not recommended. A lot of the vocabulary is drawn from Wade's grammar book-- which I would like to add is truly excellent. I was studying a lot from Modern Russian but the exercises were dull and it did not have a key. Add to that the fact that it is quite old and I found myself looking for something fresh with enough advanced grammar to improve my Russian. Well Wade's book goes above and beyond covering nearly every aspect of Russian grammar ever conceived. You name it and it has its own section with detailed examples and explanations.
All in all, I think the two are inseparable and will give the serious student of Russian that extra boost they have been looking for. This will truly help you master the nuances of Russian grammar.