The genus list. A few dozen pages and counting filled with info on every single diagnostic Mesozoic dinosauromorph that was known at the time of writing. This is the most complete dinosaur encyclopedia indeed. Did we mention that it has every single diagnostic Mesozoic dinosauromorph that was known at the time of writing?
The way the book keeps reminding you that birds are dinosaurs. Other books may touch upon the subject, but they tend to gloss over it or add it as an afterthought. This one doesn't beat around the bush. "Birds are dinosaurs, people, and don't forget it!"