This was the book my mentor told me to learn from. I had a really hard time reading this book at first. As a beginner, this book felt so hard to read, as if it was not meant to be read for a newbie like me. But he keeps emphasizing on how important the contents in this book are for me, and for other beginners. After going through about half of it, I finally understood why he said so. This book contains all the fundamental knowledge (system administration, os, networking, some hardware, and operations) to get you started in the tech industry. It covers so many things in 1200 pages. But It lacks graphs, diagrams, and pictures since it is an old book. But I highly recommend anyone working in tech to read this book. It will be extremely beneficial for your career, or purely for educational purpose.
I found this book from a website that recommends 10 books to learn CS from. This is a really awesome open-source book. You can read it for free in the link that put inside the title. It contains fundamental knowledge on operating systems. I have only read half of the book, and it already gave me so much insights on how operating systems work. I highly recommend it, and will definitely re-read it again in the future.
This book is pretty much similar to the operating system book. It just talks about different topic which is computer networking. It's not free, but it has better graphs and pictures. Contents are as awesome as the previous books. Read all three and you'd have a really good fundamental knowledge in tech.