Dark Souls III: Design Works is a nice art book with lots of large, high quality concept art from the game. There are a handful of pieces from each area, each enemy, each boss, each weapon, etc. What's missing is accompanying text and interviews!
Previous Dark Souls Design Works books had long interviews with key staff who worked on the games and provided fascinating insight into their development. This one has none of that. Other than the name of each area/boss/etc., there's virtually no other text, which is a real disappointment.
If you just want to see some art, this book is great. But if you want more than that - if you enjoyed the deeper look into Dark Souls development provided by the first two Design Works books - this book will be a big letdown.