DevOps is a broad topic. From my personal book shelf I would recommend (in addition to Matt Stratton's suggestions!)

• The DevOps Handbook: How to Create World-Class Agility, Reliability, and Security in Technology Organizations
• Continuous Delivery: Reliable Software Releases Through Build, Test, and Deployment Automation
• Production-Ready Microservices: Building Standardized Systems Across an Engineering Organization

Also the following additional resources are good for creating highly maintainable and reliable applications:

• 12 Factor App
• DevOps Metrics 101 - requires free subscription to Agile Alliance