This is a very good product, though the CD is unusable without the book. I don't know enough Farsi to comment on the pronunciation and usage, but contrary to what another reviewer has said the Colloquial series is usually less academic than the Teach Yourself series. In the Teach Yourself series, there is more polite sometimes unusable language. In defense of the Teach Yourself series, the CDs can be used more easily without the book, as there is an English-speaking guide (which is lacking on the Colloquial CD). The Teach Yourself and Colloquial Persian series are quite comparable--both good. The best layout, however, belongs to How to Speak, Read and Write Persian (for which I do not have the CD).
I don't think it would be a mistake to buy any one of the above-mentioned. However, if I were to buy only a book, it would be the last book I mentioned, as the Farsi font is thinner and easier to read, plus the book is bigger (L x W).