Is a very beginner book, the first 4 chapters are bored for someone that as a background in programming. From chapter 6 begins the real examples, but are so easy. it take at most one hour to complete each example. Although are good examples to practice the skill, and learn some things.
The book lacks much on scripting, 2D Animation, GUI, etc... Enter to a intermediate level of development a game with Unity. Exists best content on the official page of unity.