I am the author of the book, "Terraform in Action" recently released through Manning Publications. This book is intended for anyone who wants to improve their skills with Terraform and learn current best practices and architecture principles. It's divided into three sections, the first gets you to learn the foundations of Terraform as quickly as possible. The second section covers real world use cases in three different clouds (AWS, Azure and GCP) and the final section covers advanced Terraform use cases, as well as what you would need to know to be a Terraform SME/ TFE administrator.
Terraform is an increasingly important technology for managing Infrastructure as Code (IaC). Anyone in the DevOps/SRE space will definitely need to know Terraform, but also anyone who uses the cloud, or works heavily with APIs could benefit from learning Terraform.