Ruby Language

O'Reilly Media

The Ruby Programming Language: Everything You Need to Know

Packt Publishing

Polished Ruby Programming: Build better software with more intuitive, maintainable, scalable, and high-performance Ruby code

Pragmatic Bookshelf

Programming Ruby 3.3: The Pragmatic Programmers Guide

Independently published

Ruby Programming for Beginners: An Introduction to Learning Ruby Programming with Tutorials and Hands-On Examples

Addison-Wesley Professional

Eloquent Ruby [Lingua inglese]                  

Ruby Programming Language: A Concise Manual For Quickly Learning Ruby (English Edition)

newhmapps

Learn Ruby language                              

Ruby Programming Language: Comprehensive Ruby Programming Language Guidebook for Beginners and Advanced Learners (English Edition)

Ruby Languages: Discover The Languages That Ruby Is Coded In (English Edition)

Cheat Sheet for Ruby Programming Language: Written by Navis Michael Bearly J (English Edition)