There are a large number of beginner's Ruby resources out there, and the material is diverse. Here are a few places to get started.
This isn't actually an e-book, but an interactive tutorial. It runs on Windows, OSX or Linux. It's designed for kids, but anyone can learn to program using it. We covered it here previously.
It was created by _why the lucky stiff, something of a legend in the Ruby scene. _why disappeared from the Web in 2009, and Steve Klabnik has taken over the project.
_why's (Poignant Guide) to Ruby
Also by _why, this illustrated guide to Ruby may be totally engrossing to some readers and too outlandish for others. It's straight-forward, and easy to read but contains many cartoons and completely unrelated sidebars. I've never seen a programming book like it.
_why deleted the book when he exited the Internet, but there are many mirrors. This seems to be the best place to find it.
Mr. Neighborly's Humble Little Ruby Book
Another quirky beginner's guide is Mr. Neighborly's Humble Little Ruby Book by Jeremy McAnally. This one is a little more conventional than the Poignant Guide, but still contains a strong authorial voice.
Programming Ruby: The Pragmatic Programmers' Guide
If you're tired of quirk and just want a big, meaty guide to Ruby check out Programming Ruby: The Pragmatic Programmers' Guide from The Pragmatic Bookshelf, frequently referred to as "Pickaxe." It's considered by many to be the definitive guide to Ruby, and the first edition available for free. The updated second edition will cost you, however.
Learn to Program
How To Think Like a Computer Scientist: Learning With Ruby
How To Think Like a Computer Scientist: Learning With Ruby by Elizabeth Wiethoff is a Ruby port of Allen B. Downey's How To Think Like a Computer Scientist series. It's not yet complete. Other variants can be found at Green Tea Press. The Python version of the book has been used by MIT for an introductory programming course.
- The Little Book of Ruby by Huw Collingbourne - A concise beginner's guide to Ruby published for free by Sapphire Steel, the makers of the Ruby In Steel IDE for Visual Studio.
- Ruby Essentials
- Ruby in Twenty Minutes