The author has put together an interesting and compelling low-magic fantasy setting.
The people that inhabit Sonu are well crafted fantasy races that will feel familiar enough to fans of the genre while avoiding some of the common and often worn out elf/dwarf/halfling tropes. The history of these races, and the conflicts among them give life and tension to the setting. It's pretty awesome.
There is ample room both geographically and lore-wise for lots of fun and unique adventures to be had. That said, the 4 provided adventures are thorough and rich and could stand on their own as a short campaign, or be highlights in a much longer campaign in which the game master could flex some creative muscle.
The content is well laid out, and the artwork is very nice.
I'm going to have to pick up some more of the titles available, and introduce my players to Sonu. I think you should, too.