I think it's a great vehicle for introducing the total novice (like me) to the world of Terrinoth. I need artwork to sort of immerse myself into the feeling of a setting. I love sweeping, visually complex or narrative art pieces to help me see what the world is like. I hate something being described as "a tall humanoid made of iron, covered in runic wards and glyphs, wielding a halberd in one hand and a shield in the other"; actually SHOW me a picture of an Ironbound.
The book provides supplemental rules for fantasy tropes and themes, but the book is a showcase for someone to run a Terrinoth game. I feel FFG did a great job with this book and look forward to similar treatises for Android, Twilight Imperium, and especially Tannhauser.