It doesn't really require a knowledge of ruby, so you might want to have a look.

From the FAQ on the front page:

Do I have to know Ruby?

Really, I love alliteration: the only thing the 'for Rubyists' really means is that I assume you don't know about pointers, concurrency, or similar things. That's okay, you've never had to think about them before! I explain this stuff in extra depth. If you program in another dynamically typed language, you'll be just fine. If you program in another systems language, you'll be more than fine.