A couple of years ago I bought my younger brother Chris Pine's "Learn to Program" (with Ruby), and he's finally gotten around to reading it. And appears to be enjoying it.
This is something I'm keen to encourage, so would like to know what's next? I don't want to confuse him with another language, so something Ruby would be ideal.
Cheers.
The Pragmatic Programmer has several good books on Rails, my favorite of which is Agile Web Development with Rails. There's also Programming Ruby (the Pickaxe book) and many others.
I know "Learn to Program", but I do not know how detailed it is. However I think Rails or other (more or less) sophisticated frameworks are definitely too complex for a beginner and would rather demotivate him. In fact it depends on his style.
If he wants to know more about the language and the constructs he can use in Ruby, then "Ruby Way" by Hal Fulton (as written by IDBD) is definitely a good source. It explains all kind of code pieces and recipies. But it is organized around solutions, so all chapters are organized in "how can I do ...". This would be very helpful when he has an idea of a little fun project he would like to do. But to be careful, Ruby Way has 800 pages, so it might overwhelm a newbie.
On the other hand, if he enjoys learning by doing, I can recoment "Ruby Quiz" by James Gray II. It is very nice as it contains a lot of little funny problems together with solutions. I enjoyed playing with it, but was no beginner any more. All questions could be done by a beginner nevertheless. There is a website with more quizzes that you could try upfront.
"Everyday Scripting with Ruby: For Teams, Testers, and You" (also a pragmatic programmers book) is a nice book. It uses real world examples (most of them simple, but the watchdog framework is reasonably complex), which is a plus for me.
I wrote a small tutorial aimed at people who wanted to learn without being spoonfed, by actually doing something. The theory was that having the answers handy was demotivating as far as actually making a determined effort to solve the problem yourself went.