McDermott Wes. The Comprehensive PBR Guide by Allegorithmic. Volume 2

Light and Matter : Practical guidelines for creating PBR textures

Cover by Gaëtan Lassagne, written by Wes McDermott
Technical edit by: Nicolas Wirrmann and Jeremie Noguer
Copy edit by: Alexandre Bagard

What is PBR?
Metal/Roughness Workflow
Specular/Glossiness Workflow
Maps common to both workflows
Substance PBR Utilities
Appendix - Charts