for engineers
I recently rediscovered Volume II, which I got over a decade ago after it was thrown out at work. I saw a good deal for the first volume on ebay and took it.
Being from the 1960s, it's kind of obsolete, but kind of not. A lot of general engineering tasks haven't really changed much, it would probably be fine to consult for things like bolted connections, gears, hydraulics and such. Obviously it's missing anything related to modern electronics. On the other hand it has chapters about extremely cool stuff like steam engines! And no CNC machining, but if you're a hobbyist with an old manual lathe or milling machine, you'll find some relevant knowledge here!