Refactoring Ruby Edition is a book about Refactoring. with a list of code smells and techniques to changing the structure of ruby code without changing it's behaviour. Website 
Amazon
This is based on the original book Refactoring: Improving the Design of Existing Code, but rewritten with the Ruby language in the examples.
This is a must-have book for any professional developer and lists techniques referenced in 99 Bottles of OOP.
This book is similar to Dive into Design Patterns which introduces patterns with pseudo code rather than Ruby.
If you want to see how this could be applied, I recommend reading 99 bottles first then coming back to this.