This book is not for biginners on Vala programming. You should go to http://valadoc.org/ to find resources about Vala.
Some introduction about how Vala builds C code is explained in order to help to better understand how Vala works and how take advantage of it without die on the road.
This book will resume some tips and tricks on using Vala on your applications and libraries, you should take in account. They will help you to avoid most common errors and problems.