I used the famous Pickaxe Book (
http://www.pragprog.com/titles/ruby/programming-ruby), but I think it's not very good nowadays. Like all the programming books I read, it was okay for people who already know another programming language.
If you do not know any programming at all, but you know anyone who does, it's usually the fastest to ask him or her to explain the basics to you. Variables, functions/methods, "if", "while", "class" are similar in most programming languages and the Gosu example programs only use very, very basic Ruby.
I am curious though, does anyone have any experience with this book?
http://www.pragprog.com/titles/ltp2/learn-to-program-2nd-editionI have lots of people ask me how to get into Ruby as a first language, but honestly I don't feel like recommending the Pickaxe.
And then there is
http://mislav.uniqpath.com/poignant-guide/ :)