Having already bought and been thoroughly impressed with Routledge's Polish: An Essential Grammar (also by Dana Bielec) I had no hesitations about coughing up more cash for another textbook from the same author and publisher.
The Essential Grammar is more of a handbook to Polish, a reference book, whereas this Intermediate Polish is a workbook. It is split into 40 brief units, each of which starts with some material covering the grammar, which includes plenty of examples to get meaning across sufficiently (and provides useful notes on nouns linked to certain verbs - ie, from the same root). Each unit then has a number of exercises designed to test the specific area of grammar taught in that unit.
There is a key at the back for all exercises (although I have found a couple of errors, 99.9% of the key is correct), and useful appendixes covering pronouns, prepositions and other common areas of difficulty for foreign learners of Polish, all of which are clearly laid out and explained.
The introduction to the book recommends studying units 1-4, then revising units 1 and 2; then studying units 5 and 6 and revising units 3 and 4; and so on. I've found this a useful method and have followed it. A lot of the units complement each other, and grammar used in earlier units reappears in later units. The whole book also provides a useful revision of case endings, which are tested incidentally alongside other grammatical material, but not actually explicitly taught. If you haven't learnt case endings yet, and basic past and future tenses, you would probably be better off getting Routledge's (and Bielec's) Basic Polish.
With a language like Polish, with its stacks of exceptions to rules and fairly complex grammar, it is of paramount importance to explain things extremely clearly and provide learners with plenty of opportunity to practice. This book does both of those things excellently. Here's hoping an Advanced Polish book is to follow.