Not sure if this has been mentioned somewhere yet. TWIL usually covers stuff like this but I’m way behind on those episodes.
https://www.humblebundle.com/books/unix-linux-books
Lots of good stuff there for newbs and veterans alike! 16 books for less than the cost of one hour at my local Virtual Reality arcade. What a steal.
I didn’t know about this one yet, thanks Ethanol. For those who’d like to use an affiliate link. . . https://tuxdigital.com/go/humble-unix-linux-books 
I took a look and some of the books are very old, as in 15+ years old.
I did get a bit suspicious when the Linux Driver book did not even mention PCIe. Then looking further, I see titles are so old, they released them into Creative Commons.
Yikes! That’s pretty old! I wonder if it’s still relevent at all.
I didn’t check all of the books, only a couple of them, but you know the old saying “if a deal sounds too good to be true, it probably is”.