Not a bad shallow introduction to the package structure, but it leaves out more than a little, and doesn’t address compiled software at all.

Fortunately, Debian has extensive documentation.

https://www.debian.org/doc/devel-manuals

The New Maintainers’ Guide might be a good next step for understanding more use cases and available tools. (From a quick glance, it looks only a little dated.)

The full Guide for Debian Maintainers is more up to date, including relatively new tools like dh that considerably simplify packaging software that uses common build systems.