The Book of Ruby: A Hands-On Guide for the Adventurous
"Conventional wisdom has suggested that the so-called 'Pick-Axe Book' (Programming Ruby by Dave Thomas) is so good that there is no room for other options. I prefer Collingbourne's book. The Book of Ruby is a clear, easy read ... with the end result of having good working knowledge of Ruby." (Andrew Binstock,Dr Dobb's Journal)