They're by no means perfect, but we try to be super open about our development process.
Many of the github issues also have comprehensive discussions of topics, searching the repo for topics you're interested in will often surface interesting discussions.
If you want to get more deeply involved, I'd suggest the Kubernetes community meeting (Thurs, 10am Pacific)
Are you guys still working on the documentation ? I tried to setup a test Kubernetes cluster for a recent hackathon and couldn't get it to work. minikube kept cribbing that 'host only adapter we created cannot be found' ( I think this error is from docker-machine ) and the vsphere tutorial failed while trying to upload the vmdk file.
Oct 2015 was when the first preview went live. Not sure when the last release went out but my copy is missing 3 chapters at the end on deployments.
This book does the same re GCP with most stuff done via the gcloud CLI that I've seen anyhow(I've only skimmed the book). Pretty sure Kelsey Hightower works for Google so it makes sense it is specific to their products.
Your wish is my command! https://kubernetesbootcamp.github.io/kubernetes-bootcamp/