Grow in ICS Security | SANS Institute
www.sans.org
The ICS Security Field Manual series comprises several volumes, each focusing on a different aspect of ICS and security defense for control environments. The manuals will cover what these systems are used for, how we rely on them, how they are attacked, and practical ways to defend and protect our critical infrastructure.

You have to give some personal info to download these, but SANS ICS published 3 PDF “field manuals” that discuss ICS security topics. They’re pretty good for reference and/or to provide a high level overview of ICS-specific considerations for security!