Apprenticeship Patterns http://www.amazon.com/Apprenticeship-Patterns-Guidance-Aspiring-Craftsman/dp/0596518382
Practical Object Oriented Design w/ Ruby http://www.amazon.com/Practical-Object-Oriented-Design-Ruby-Addison-Wesley/dp/0321721330
Clean Code http://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882