This is a guide to Russian usage for those who have already acquired the basics of the language and wish to extend their knowledge. Unlike conventional grammars, it gives special attention to those areas of vocabulary and grammar which cause most difficulty to English speakers, and focuses on questions of style and register which are all too often ignored. Clear, readable, and easy to consult, it will prove invaluable to those seeking to improve their fluency and confidence in Russian.
Seriously great, a comprehensive and consummate reference and pedagogical work: if you have an intermediate to advanced command of Russian but are not a native speaker and especially should you be planning to travel in Russia, this is such a useful book. You learn how contemporary Russian is actually spoken, actually used. Granted, the book is six years old now, so you may not garner the very latest slang, but for business purposes and such, you will understand how everyday Russians use the language. This book has prevented me from seemingly a noob or a clueless American many a time in spoken and email communications alike, plus, it's just very interesting to read.
I also have the same book by Oxford for Spanish, however, it's not nearly as good: the author, Prof. Derek Offord, did a stellar job in writing the Russian one but whoever did the Spanish one wasn't on top of their game for whatever reason.