2.5 Not a bad read as such, but the first part is meanderingly uninteresting and even the big expedition (what a spoiler!) is less interesting than all the limited forays in the books before. The last fifth or so (if you're generous) picks up somewhat and has one really interesting revelation, albeit one that is quickly resolved to cap off the trilogy.

While the different cultures' magic systems come across as believable and actually different, I feel somewhat uneasy about this whole painting with broad strokes. Maybe I am wrong and the author consulted some people knowledgeable in these matters, but splitting any cultural thing as broad as European, African and Asian leaves a bit of a bad taste. Taken together with completely eliminating Native Americans and not even mentioning the fact that there could have been people (what-if-ing being a large part of alternate history) sort of make me regret reading the series - or at least shelling out that much money for physical copies.

On the plus side, the extremely predictable romance is very toned down, there are some more cool female characters (though they tend to marry) and some of the magic is quite original. Unfortunately, LGBT stuff is there only in the most deniable way and handicapped people don't really seem to exist. The book is very good on women's issues and generally paints a realistic, but thanks to magic and frontier life somewhat improved picture as opposed to our timeline.

All in all this is a book that you can read, but don't have to. Not really comparable to the first volume.