I was surprised when I saw this posted on the Paizo Store Blog and after looking at it, bought both this item and the adventure. Using the world as we know it as a fantasy setting has been something I've been doing since the late 1980s and I was intrigued to see another person's take on the setting.
Overall, the quality of the product content is very good. Grammar is good, typos are pretty non-existent, and the prose is clearly written in a fashion that says, "game supplement" rather than "history thesis". The characters shown in the art are suitable for the era portrayed.
Overall, I liked it but was left wanting more historical background, cultural background, and explanations that satisfied or answered the faults I had with the product.
First, the dating system. Why is it using a Christian based dating system when there was no Christ or Christ event?
Second, the political groups. Many of the political groups came about due to how Europe developed hand in hand with Christianity, the Islamic invasion, the Roman successor states, and the clash between Christianity and the old religions.
Third, how the non-human races fit in. It seems like they're afterthoughts and not integral parts of the world.
Fourth, how the monsters influenced geopolitical development.
I guess what I was hoping for was something more along the lines of the cultures being used as the basis for the nations and groups rather than specific historical governments shoehorned into a fantasy setting.