It's still in "raw" status, but the release date says October 2015.

These days, with 3-6 month release cycles, I can't see how a traditional publisher could stay current unless you have a rapid iteration cycle.

Also, I wonder how platform-agnostic the book is? I know many resources out there start by having you set up a GCP account.

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.