Is there a book about Ruby On Rails for someone that has little or no understanding of Ruby?
Although Ruby On Rails is a great reason to start learning Ruby, I’d be bored out of my pants if I first have to read a full book on Ruby and then a book about Ruby On Rails.
Something that demonstrates the basic principles of both Ruby and Ruby On Rails would be an ideal intro to this world.
Agile Web Development with Rails (Thomas, Heinemeier Hansson) is a good intro to rails, and introduces Ruby gently along the way, you don’t need to know ruby to read it.
http://www.amazon.com/Agile-Web-Development-Rails-Programmers/dp/097669400X