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.

I thought this book was excellent. I enjoyed the narrative-focused structure of the game, especially the idea of One Unique Thing and backgrounds. The classes are also extremely unique and the world presented in the book in engaging. I have also purchased the 13th Age Bestiary and 13 True Ways and have been consistently impressed in the quality across all three books. There are tons of good ideas and the system seems tightly focused - the rules have purpose and focus on creating a good time at the table.