It's a really detailed setting and you can see that a lot of work was put into it. For a foreigner like me, the history of the city was completely new and easily understandable. Frequently in products like these is hard to feel like you understand the setting without some painful hours browsing wikipedia. This one skips that part. The author also told me that she is working on getting some pronunciation help into the books for non-french people.
The one thing that could be a problem for some people is that the art has some minor inconsistencies here and there and every few chapters you catch yourself wondering "where have I seen this before?" This is very minor and doesn't take away from the experience. The book is worth getting for the dozens of npcs alone and it's a really good tool to have for moments in which you need to conjure someone out of thin air for a story but can't quite figure out where to go.