I had this book on my wish list at Amazon for awhile (on account of the title and reviews there), until I saw the book and flipped through it at B&N.
It looked ... well, not really useful. I couldn't tell who the audience was - if it was for Pagans, its section on "errors in the Bible" seemed to me to only reinforce the erroneous notion that many Pagans have of all Christians being legalistic fundamentalists. Additionally, this chapter seemed to encourage the notion that Pagans should feel free to "dish out the same" to fundamentalists, when I think that such serves no purpose. Knowing a list of factual errors in the Bible without understanding the culture and tradition where it is read means that in many cases, people are apt to misunderstand the traditional interpretation of such verses and get just as tangled in their own arguments as fundamentalists are in theirs. Also, for Pagans, it presents a pretty simplified Christianity - I'm not sure that one would come away with a better understanding of the religion.
It concentrated too much on talking about Wicca (and didn't discuss the wide variety of other Neopagan religions), and if the audience was Christians, I think they'd find the book a bit too much on the order of "Pagans and Christians really believe the same thing" - the book seemed to gloss over the differences between the two religions, which I suspect some Christians would find disrespectful. Also, despite the title, the book only discusses Wicca, and ignores the wide variety of other Neopagan religions. As a Neopagan, I don't feel that a Christian reading this book would have any idea what my religion includes. Additionally, parts of the book are antagonistic to Christians, and verges on blaming them for oppression of Neopagans. I suspect would be a turn-off to those reading it. And finally, liberal Christians probably agree with many of his points already, while fundamentalists are unlikely to ever read the book.
I didn't come away from reading a couple of the chapters and skimming over the others with any sense that by reading the book carefully, I'd gain insight either into Christianity, Neopaganism, or any particular person's personal spiritual experience. I think the book tried to do too many things at once, and ended up not really doing any of them well.