SaphireSteel.com gave away the free book The Little Book of Ruby and I took advantage of it. Due to some things I was working on I had to restart the book several times. Now that I've finally finished it I thought I'd write up my thoughts.
The Little Book of Ruby does a decent job of explaining the very basics of Ruby. It does not delve into detail or give best practices on things, however, it's enough that a Ruby Beginner can read through the 85 page eBook and be able to figure out mostly what's happening in Ruby code that they look at.
It's a better start to Ruby than Why the Lucky Stiff's into. Why is an interesting character, but he gets too sidetracked, The Little Book of Ruby is a much better starting place.