I have a Unix System V textbook in my bookcase. I’ve never cracked it open. Also Linux for the Compete Idiot which I have read but haven’t referenced in almost a brace of decades. Then there are a couple Adobe products texts, probably for Illustrator and InDesign, but I’m too lazy to get up and read the titles. I advanced beyond them a long time ago. These days the internet produces answers a lot quicker than I can look it up in a book.