I don’t even know why Ruby was included in this book at all. Seriously I would consider taking it out and putting one of the other candidates in instead. Programers know Ruby already. It is probably one of the most well known language. And this is do to no small effort of yourself (Bruce Tate… who was responsible for me getting into Ruby in the first place with your gutsy book “Beyond Java”). As well as the hard work of Andy Hunt, Obie Fernandez, Dave Thomas, David Black, Hal Fulton, David Heinemeier Hanson, David Flanagan, Peter Cooper, Kevin Baird, Brian Marick, Russ Olsen, Mike Clark, Michael Hartl, and of course Matz, and dozens of other authors… oh yeah… and some guy named Jim Weirich. :) Ruby is well covered.
Pick another OOP language. One, like the rest of the languages in this book, that shows real potential, but never really enjoyed a spot light moment.