The repositories are as follows:

• bookshelf is the main sample repository for App Engine, Cloud Run, Compute Engine, and GKE deployments.
• bookshelf-function is the modified version of bookshelf that allows the Express app to be hosted in Cloud Functions.
• bookshelf-greenlock is modified version of bookshelf to integrate Let's Encrypt within the app layer.
• functions/hello-world is just a sample Hello World Cloud Function.

You may file an issue with the book or with the sample code in Issues.