Not that that is a bad thing, just that if you've programmed in almost any imperative language you're fine reading that online book. I'd love to use rust to replace my C stuff in the future if possible once it stabilizes. But until then I am just popping back to that book every other even .N release to have a look-see at progress.
It's basically a tutorial for people coming from typeless, pointer-less dynamic languages, whereas the official Rust tutorial assumes familiarity with the concepts that a C (or C++, C#, Objective-C) developer would know
Hopefully I will have something better and more generic near the 1.0 release ;)
Plenty of people are suggesting Rust for Rubyists, which is a good resource. I personally found it too simple, which is not a reflection on the resource but instead what I was looking for. It is likely to be exactly what plenty of people are looking for.
I wanted to give some motivation for keeping on at the official tutorial. Some of its contents went over my head initially as well, but I read it again a couple of weeks later, and everything clicked into place. It's a really awesome guide to the language, and the links at the end to guides to various more specialized parts of the language are similarly awesome.
At some point (shortly after the 0.9 release?) one of the first examples stopped working with a then-current git build, so I stopped reading it and concentrated on the official tutorial more.