Ruby User's Guide
by Mark Slagell
Ruby is "an easy object oriented language". It may seem a little strange at first, but it is designed to be easily read and written. This User's Guide will get you started at invoking and using ruby, and give you insights into ruby's nature that you may not get from the reference manual.
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by Zed A. Shaw - LCodeTHW
The book assumes absolutely no prior programming knowledge and will guide you carefully and slowly through the learning process. When you are done with it you will have the skill to move on to other books about Ruby and be ready to understand them.
by Mitch Guthrie - bigfatrails.com
A book designed around teaching Ruby on Rails in a precept upon precept fashion. Both theory and practice driving your knowledge. If you are a beginner, the purpose of this book is to simply get you there in small, manageable steps.
Everything from installing Ruby and the basics of the language through to topics such as arrays, file handling and object-oriented programming are covered. Written both for experienced in other programming languages and for novices.
by Jeremy McAnally
Covers the Ruby language from the very basics to the advanced topics. Written in a conversational narrative rather than like a dry reference book, Mr. Neighborly's Humble Little Ruby Book is an easy to read, easy to follow guide to all things Ruby.