The Well-Grounded Rubyist is my favorite Ruby book because it really drives home just how internally consistent the Ruby object model is. It gave me a deep appreciation for the aesthetics of Ruby.
This. Ruby’s syntax sugar makes it easy for newcomers to miss the elegance of what’s actually happening with everything being an object and every expression reducing to passing messages between objects. When you dig in and really understand what’s going on, the lightbulb moment is very neat.