Wicked Cool Shell Scripts (2004)
Read in 2020.
I read the second edition (2016), cursively.
If you all do is admin on a handful of systems, this is a good resource. It’s very will written for its approach, but the approach is flawed. If you want to write reliable shell scripts, prefer Pro Bash Programming: Scripting the GNU/Linux Shell (2009), which deals much more effectively with the principles. If you want to package your tools to have them version-managed and at your fingertips on arbitrary remote hosts, or shuffle data, neither book will help you much.