We just went through six chapters of intense coding. It is easy to forget what it was all about a hundred pages ago, so let's quickly summarize the journey we are almost through.
Chapter 1, Infrastructure Automation, was not entirely about Terraform--you've learned a few general principles of modern infrastructure automation and, more importantly, you get to learn what Infrastructure as Code (IaC) is. If you want to have a success in doing modern operations, understanding IaC in depth is a must. This book only covers one particular tool, so you need to do some extra reading to really master ideas behind IaC. Perhaps the most comprehensive work on this topic is a book titled Infrastructure as Code: Managing servers in The Cloud by Kief Morris.
In addition, check out Infrastructure as Code (IAC) Cookbook by Stephane Jourdan and Pierre Pomes that has many practical examples of different IaC tools, including Terraform.
That very first chapter also...