I'm only on chapter 2, but holy cow this is an amazing book! It's a very conversational, "Hey, you're new to coding? No sweat! Let me show you the ropes of this awesome game engine called DragonRuby while I walk you through building your first game." It's casual and charming enough to keep me interested, while also not taking forever to get to the next point. And best of all, it's FREE! 

(I'll wait until I've gone through more of the book before I bump the rating up to 5 stars. )