Some of these old books have some gems of information in them that you just won't find in modern books. Things like hardware schematics are commonplace in old programming manuals. In the 8-bit era it was usual to cover everything from assembling the computer to programming it in the same book. There weren’t dozens of blogs posts and “for dummies” books either: the manual was it. It had to cover everything.
Then there are the useless factoids, my favourite of which is that Tron is actually a command from old versions of Basic: TR(ace) ON. There is a corresponding but less cool-sounding TROFF command. I was rather disappointed that the names in Tron Legacy were all random nonsense, presumably because nobody involved realised that that the names in the original were all real computing terms from that era.