I read the reviews about the historical accuracy of this book, and the one thing that stood out among the naysayers is that no one recommended a more accurate or better book.
There are many books on the Goddess, but few that contain so many in one volume, and few that try to cover a broad range of cultures and themes. For example, you can buy books about Mother Goddesses, or Goddesses of a particular culture. Most books on the Goddess cover fewer Goddesses. In order to rival the information covered in this book, one would need to collect Goddess books for years.
However, if you wish to focus on one Goddess or one culture, this is probably not the most helpful book for that purpose. In my opinion, this is more of a "big picture" book.
Regarding the historical accuracy of the book, my perception is that this book was written through the lenses of the Wiccan belief system, using what historical information was believed at the time.
It was first released in 1987. My copy was printed eleven years ago. Since the first release, there has been a firestorm of debate over the historical accuracy of much of popular Pagan beliefs.
I think that it's helpful to remember that while we do need to understand Paganism with historical accuracy, we also have the power to create a new myth. We just need to understand the difference. Just my opinion.
I think this item is a classic and a staple on nearly every Pagan bookshelf. Even if you don't agree with every single statement made in the book, it's good to read it just to know what the fuss is about.