For tutorial/walkthrough with lots of example small scripts Beginning Ruby, 2nd ed by Peter Cooper. For a straight reference The Ruby Programming Language by Da

For tutorial/walkthrough with lots of example small scripts Beginning Ruby, 2nd ed by Peter Cooper. For a straight reference The Ruby Programming Language by David Flanagan and Yukihiro Matsumoto. A middle-ground (tutorial first half; reference second half): Programming Ruby 1.9 (aka, the Pickaxe Book) by Dave Thomas. A great second book (maybe even first if you're comfortable enough learning basic syntax on your own) is Eloquent Ruby by Russ Olsen.