May be I did not look in at the right place, but I have been trying to find a good book on Ruby since I started learning the language, and have not found one yet. Can you refer me an affordable quick reference kind of book on this language?
why not try Agile Development With Rails, 2nd ed? It's moderately priced at around $15 - and is a great guide book. The first half has you building a web-app with Rails, the second half goes in-depth covering the different framework components. I've found it to be very useful.
I think our book stands out because it answers a question that few books actually ask: "I know the language...now what?" Very rarely are there practical thoughts given to what you can actually do with a language. Usually you're fed arbitrary code examples with little relation to what you'd actually use the language for. In this case, though, we spent a lot of time making sure that we teach you how to get things done in Ruby.
As for actually learning Ruby, I'd recommend Manning's "The Well Grounded Rubyist" (coming soon) or my free Ruby book http://humblelittlerubybook.com. The former will obviously be much more in depth, but if you don't have the cash for it, then please enjoy the free book!