[boost] [system] How are users expected to learn Boost.System?

Hi, Since Boost.System doesn't appear to have any documentation other than its reference section, I'm wondering how users are expected to really learn this library? It would be nice if a tutorial section could be added to its documentation, including tutorials outlining how to extend the library with our (the library user) own error sources. That is: when to extend, what to extend and how to extend. The unclickable "Tutorial" link currently on the library's home page almost feels like a slap in the face ;) Thanks, Lee.