Let me start with the *brief* listing of this book's virtues. If you are already comfortable with written and spoken Persian, this book has some use. Some minor vocabulary differences between Farsi (Iranian Persian) and Dari (Afghan Persian) can be picked up from the thematic word lists (i.e. using the work "tashakkor" in place of "merci" to mean "thanks), and some of the more subtle differences in pronunciation can be garnered from the author's translatirations (i.e. pronouncing the present-stem indicator as "may" instead of "mi," as one would do in Iran). So much for the positives.
This book has some major flaws. Some have already been enumerated in another review on this site, so I won't repeat theam. I want to illustrate the difficulty presented by the author's non-standard transliteration; customary practice dictates that the Persian "aleph" be transcribed as either "â," or "aa." Instead, the author has chosen to transcribe it as "'a". Meanwhile she uses the standard transliteration for the letter "ayn," which is either "'" or "a'." Not only is this confusing, I've spotted two places in the book where she herself mixed the two up.
And that leads me to my next complaint about this book. It would seem that its first draft made the press. I don't see an editor listed, only a note thanking a certain person for "insightful suggestions on the manuscript." There are numerous mistakes, not just in transliteration, but also in her Persian spelling! For a true beginner (recall the title of the book, if you please) this could produce a lot of confusion.
I can't comment on the grammar sections, having skipped them. I agree with the reviewer here who suggested reading Thackston's introductory book-- it is very technical, but *very* precise, and there is really no issue about transliteration, spelling, or translation.
If, like me, you wanted to have a textual reference to familiarize your mind with Dari, this is not what you're looking for. My best suggestion is find a native Dari speaker: many Afghans have been to Iran and could guide you through the differences between the two dialects; otherwise just listen to them speak. But whatever you do, it's not worth your while to buy this book.