The problem is that the guide is out of date in terms of toolchain, and you need to figure out many things by yourself, especially if you want to develop on Linux. My book helps you to understand how to learn and write x86 with Intel manuals (this is really important!), understand how to craft a custom ELF binary that is debuggable on bare metal, which in turn requires you to understand a bit of how debugger works.
Once you get gdb working, it is much easier to learn how to write an operating system.
There are many topics other OSes like Windows and Solaris do differently and talking about them even for a little bit would be beneficial, but I haven't seen any trace of it.
Search for Windows, Solaris, shows up nothing, and search for unix shows a single page about unix signals.
It does not focus on the concrete implementation of an OS though.