Never new Rust by Example existed until today actually! You really should link to it somewhere more prominent. I'm fairly far along, but would have loved the example book had I know about it sooner.
It was originally a community project, but was then abandoned for a while, and then donated to Rust proper. As such, it's always been sort of secondary. I plan on linking it more prominently once I've actually gone through it and cleaned it up to my own personal standards, for now I just keep CI green. As such, the text has gotten out of sync with the code in a number of places, and I don't want to mislead anyone.
Fair enough: it's definitely not a good idea to promote something half baked.
It actually took me a while to find the link there just now. I don't think "External Documentation" really imparts the right meaning. Perhaps something like "Other Guides and Resources" would make more sense?
It is actually linked to from the front page of http://www.rust-lang.org/; it's the "more examples" link under the example. But I guess that's just far enough down to be easy to miss; it's just below the fold on my screen.
