[Mithlas]

Although you have some good points, I am inclined to fall in scc's camp. I think magic should've been held off for its own book (one of, anyway). It is important where magic comes from because that can affect what its limitations are, what happens when it goes wrong, and whether it can 'go too right'. It can also provide pointers to how to group them depending on which system magic is built on.

D&D avoids this somewhat by having long lists of spells for every single class (regardless of how sensible it might be for a cleric to be unable to cast Make Whole, for example), but it isn't without some metaphysical underpinnings. There's "material realm" or arcane magic that doesn't (usually) involve outside entities and there's "contract magic" gifted from a worshiped god (or demon), has fewer failure points but tends to be more restricted.

GURPS could have benefited from some paring down and restructuring of its magic, as well as providing alternative associations so some absurdly powerful spells don't have only one prerequisite.