Do you want to quickly learn a new programming language while still having a fairly good knowledge of another, such as Ruby? After reading the official documentation and the book recommended by the community, I would advise you look at comparison lists of how something can be done in a language that you know and how it is done in another language that you are trying to learn. These two resources provide a great foundation:
Even if the new language isn’t on these sites, you can follow their plan. It will even be more effective than just watching this sites.