Not looking for a 600+ page tome, a book in the 200-300 page range or a lecture series would be optimal.
It's CMU's 15-213 class: https://www.cs.cmu.edu/~213/schedule.html
There's also a book for it, CS:App http://csapp.cs.cmu.edu/ which is a 600+ page tome filled with exercises, and the student site has all the labs that the class does like Attack/Malloc lab. The lectures are self contained enough you can do most of the labs without the assigned text but I'm glad I bought the text anyway. It's the perfect course in that you dive into x86-64 computer systems fundamentals just enough from a programmer's perspective on how to write cache friendly code, what C code looks like in assembly, how the linker/compiler works, how virtual memory works, how OS signals work, ect., but you don't go heavy into OS implementation details like you would reading an Andrew S. Tanenbaum book.