Amongst other things I'm a bit of a book worm, sometimes older books put things in a different way. The engineering units (SI vs. Imperial/US) can be confusing but the principles are usually the same. In a way when I see a stash of technical books they shout to me "hey have you seen this interesting stuff I have in my pages?? You'll love it" - interesting too are some book on maths, if taken not too seriously they are like giant puzzle books. Maths is like basic hand tools, a screw driver, pliars, soldering iron in that it is good for doing other things with. Maths won't put a shelf on the wall but it will allow you to put it in the center of an alcove/recess.