I feel that the earlier reviews of this book are a little unfair. Admittedly, if you are looking for a quick-fix guide for going on holiday, this is probably not the book for you, but if you are actually looking to learn Polish then it is excellently structured.
The units may at first seem somewhat illogical or irrelevant, but their strong point is that they present grammatical points in context, rather than simply bombarding you with grammar and then expecting you to be able to apply it. Having studied French and Spanish at school, I remember being almightily confused as to why we were taught one variation on a word in one context, and another in another, so the structure of this book is quite good from that point of view!
Polish friends of mine have told me that some of the language in this book is not particularly up-to-date, but I think this is a fault of any language textbook. Certainly, I feel that I have learnt a lot about the language in a very short space of time. However, the accompanying CD is not immensely helpful, except if you have no other source of pronunciation to assist you. As with any language, there can be no subsitute for practising with native speakers!