This is not a joke: Read the Intel manual, maybe check out some of the learning repos on github that solves all the glue-stuff that isn't important. I have one such repo here:

https://github.com/fwsGonzo/barebones

I started learning kernel internals from these books, I highly recommend all of them.

Operating Systems: Three Easy Pieces (free online) - Arpaci-Dusseau

Linux Device Drivers, 3rd ed (o'Reilly) - Jonathan Corbet

The Linux Programming Interface - Michael Kerrisk

The Design and Implementation of the FreeBSD Operating System (2nd ed) - McKusick, McKusick, Watson

Solaris Internals - McDougall, Richard, Mauro

Andrew Tanenbaums book is good for the theory. Real world is a bit blurred so it's also worth reading about some modern development like eBPF (very handy for tracing too)