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 Matt Aimonetti - O'Reilly Media
MacRuby is Apple's implementation of the Ruby programming language which uses Objective-C runtime. This book is an introduction to MacRuby. Topics covered: Introduction, The Cocoa Environment, Foundation, Application Kit, Core Data, Xcode.
by Karthikeyan A K - Mind As Lab
With this unique hands-on learning experience, you'll discover how Ruby takes care of all the details for you, so you can simply have fun and get more done with less code. This book is written for GNU/Linux (Debian distro) users ...
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 Chris Pine - Pragmatic Bookshelf
Pine teaches you how to program in Ruby with a minimum of fuss or bother. Starting with simple one-line programs, you'll see how to have your webpage send you email, to shuffle your music, to rename your photos from your digital camera, and more.