I'm using this one. It's an exact copy of a book written as a tutorial to Ruby. Most of the readers experience comes from actaully scripting in said program, or looking over the comments left by scriptors in their scripts. I knew most of the syntax I know now before even hearing about this guide.
Using Ruby is a real treat. If you want to display a graphic, it's as simple as graphic.new and specifying the directory and filename. If you think of your files in minella, your in luck. Truly OO, moreso than it's distant namesake, Perl.