Ad 12-factor. Some makers are better off not to follow everything. For example, it's fine to use server disk space for a single server. So I don't want to include it as dogma.

Ad CI/CD. You either build it yourself (and the book gives you the technical knowledge to do it) or use a vendor (GitHub/GitLab/Circle CI). I actually want to do a bit more on CI/CD, but thinking how to approach it.