Looking through my Magic book, I find it amazing how most of its content was actually rolled into the Master Edition. There is not a lot that got lost and the adventures in the book made it into the free PDF that comes with the ME.
That said, there are some interesting alternatives for Magic and some more detailed monster descriptions in it, but overall I don’t feel I’m missing any of this in the ME.
I would regard it more as a collectors item now, than a valid supplement. Content of the old book was streamlined and rolled into ME, into a simpler version of the magic system which fits into the ICRPG concept of ‘trim everything down to the bare minimum’. This way it is easy to add to it.