They're not that different, so if you're just starting out I recommend following the more stable 3.2 version. Once you've finished that, you'll be in a position

They're not that different, so if you're just starting out I recommend following the more stable 3.2 version. Once you've finished that, you'll be in a position to learn the Rails 4.0–specific material very quickly (especially once the supplementary screencast comes out).