If you want to understand Linux server “guts” well, I suggest a book like “Linux Network Servers” by Craig Hunt. Unfortunately, it’s pretty dated now, but it does an amazing job explaining the basics and internals that most modern books, IMHO, just gloss over in the best-case scenario. The coolest part about this book is that you can follow it like a how-to and set up everything in it in your home lab. You’ll learn basic networking, how to manage your network, how to monitor it, and how to set up low-level services like DHCP, DNS, etc. This knowledge could help you jump-start a network admin/engineer career. The book also covers things like Apache web server, and basic web scripting (trust me, understanding how CGI scripts work will help you as a DevOps engineer!). I think it’s good reading overall. It will give you a solid foundation to build on.
My biggest beef with study guides targeted to specific certs is that they only teach you how to pass the cert test, basically. Very rarely do they actually teach you WTF if going on, and to be a decent professional, I think it’s critical to understand how things work. I’ve seen so many RHCE/RHCA people who get completely lost with basic tasks like changing firewall rules or network adapter configs on an Ubuntu, Debian (or anything other than Fedora/RedHat/CentOS/Alma/Rocky/Oracle Linux Server), because they literally only memorized/practiced how to do these things on a RedHat box and are incapable of extending their knowledge to any other OS. There’s zero understanding of underlying principles. Don’t be these people!
OK, I’m done ranting now. Good luck with your studies. Oh, and if you want a copy of the book, shoot me a DM.