The Khronos Group seems to be making another big push for Vulkan API adoption lately, after putting up an official GitHub repository of code samples they've now done a Vulkan Guide.
Another joint effort between Khronos members, with an aim of it being "the perfect place to get started with the API". It's aimed to be a mostly light read, that links to many other helpful resources for learning Vulkan development. They say it's "intended to help better fill the gaps about the many nuances of Vulkan".
You can find the guide here on GitHub.
I do find it interesting on the timing of all this, with Google's Stadia game streaming service coming up later this month which uses Debian Linux and the Vulkan API. They did say before that their code samples repository was done due to requests, so it seems likely that they're seeing an uptick in interest.
All good news for Linux of course, Vulkan is an open and cross-platform API that can give great performance for Linux games.