I thought this book was fantastic. The setting is chock full of interesting locations, cities, plot hooks, and potential quests. The book did a great job setting the tone of the setting and helping GMs come up with ideas for adventures.
Some criticisms: some of the terminology (e.g. "combat advantage") are not quite 5e-standard, as are the monster statblocks. Some of the mechanics are obviously from other systems and don't make much sense in 5e, so overall the conversion is a bit spotty at times. However, since this is primarily a setting book I personally ignored/modified many of the inconsistencies and just used the gobs of awesome flavor and background in the rest of the book.
[5 of 5 Stars!]