Brian Marick learned Ruby in 2001 because Dave Thomas and Andy Hunt, original authors of Programming Ruby, wouldn't let him off a shuttle bus until he said he would. He's been programming in it ever since, and he's made a special effort to teach it to software testers. His previous book is Everyday Scripting with Ruby, which began as a tutorial for those very testers.
He's not a Ruby programmer by trade. He makes most of his money as a consultant in the Agile methodologies. (After getting off the shuttle bus, he was one of the authors of the "Manifesto for Agile Software Development".)
"I would recommend the book Everyday Scripting With Ruby book to anyone that would like to jump in and learn programming. Its a great reference manual source, and it has excellent tutorials."
--Dion Ramos, ChicagoRuby.org