The book dedicates two chapters to Scratch. The first is an introduction to Scratch, taking you up to creating your first program. The second chapter explains how to make the space shoot-em-up Martian Attack (see project file below, and link below).
This 74-page free sample from Raspberry Pi For Dummies includes the first two chapters, introducing the book and the Raspberry Pi, plus Chapter 10, the first chapter on Scratch, in full.