While there is no single, authoritative "free" version of the comprehensive Salesforce DevOps for Architects
A DevOps Architect must champion Package-Based Development (often referred to as Modular Development).
If you have purchased the physical or Kindle version of the book by Rob Cowell and Lars Malmqvist, you can claim a DRM-free PDF version for free from Packt Publishing .
"Salesforce DevOps for Architects" is a comprehensive guide that focuses on the intersection of Salesforce development and DevOps practices. The book aims to provide architects, developers, and administrators with a thorough understanding of how to design, implement, and manage scalable, secure, and efficient Salesforce solutions using DevOps principles.