This book contains excellent material, which shows what way to look if you want to increase your productivity/profitability. The whole approach is very customer-oriented, which makes it possible to avoid distinguishing between manufacturing and service businesses (and thus getting lost in irrelevant details). The concept of quality the way that Crosby presents it is fairly universal to all types of businesses. This lets one see to the bottom of the quality issue, which is essential for true understanding.
I found very useful the idea that quality should be observed in all business activities, not only customer-specific (e.g. hiring, bookkeeping, etc. vs programming). If this is neglected then the firm simply does not know the true cost of quality. Seems to be so obvious, but ask yourself if you really think of it this way. Also very useful is the suggested way to measure quality in dollars, instead of indirect measurements, like defects-per-KLOC and such. After all, everything boils down to money, and that's the only real indicator of performance.
The weak point of this book is its language: it is a little bit hard to read, especially if English is not native to you. It would be much better if it were written in decent English, instead of US spoken.
Another pitfall is a somewhat free use of terminology. Thanks to this, many authors argue that the book message is not (entirely) correct, but the point is that some of its statements should not be taken literally. One needs to grasp the true meaning, which Crosby attaches to some of his words, like "requirements".
I rate that book with 4 stars only because of readability, which could be better. The contents deserves full 5 stars, and I consider it a must-read for all managers.