Refactoring and Design Patterns

Fearless Rails Refactoring

Practical Object-Oriented Design: An Agile Primer Using Ruby

Enterprise Integration Patterns: Designing, Building, and Deploying Messaging Solutions

Working Effectively with Legacy Code

11 Books Every Ruby on Rails Developer Should Read

Refactoring: Improving the Design of Existing Code

The Art of Systems Thinking

Site Reliability Engineering: How Google Runs Production Systems

Test Driven Development: By Example

Clean Architecture: A Craftsman's Guide to Software Structure and Design

Patterns of Enterprise Application Architecture