I’ve addressed elsewhere the question of whether magic in books and games should be presented as a science or as an art. I didn't come to a conclusion, other than that both forms can be fun to experience.
For example, Ursula K. LeGuin's original Earthsea trilogy (definitely not including the brutish fourth book tacked on years later) was in large part so wonderful because it evoked some aspect of what we find so fascinating about "magic." The Earthsea trilogy expressed the "magic as art" position superbly.
For the other approach, I can't think of a better example than Lyndon Hardy's novel Master of the Five Magics. There were two semi-sequels, but MOTFM nailed the premise of magic as a scientific undertaking.
Because it took a somewhat more mechanistic approach to magic (as opposed to LeGuin's naturalistic interpretation), I'm a little surprised not to have seen the concepts of magic as expressed in Hardy's book show up in some MMORPG already. For those who haven't had the pleasure, the five systems used by Hardy and their governing laws are:
Hardy's Thaumaturgy is what we usually think of as magic. Using the principles of sympathy and contagion, it's possible to move things, to transform things into other things, and otherwise manipulate one's environment. (These principles were used to great effect by de Camp and Pratt in their very funny "Compleat Enchanter" novels, as when their hero shortens a jailer's nose by forming a model of it in wax and melting it.) However, a strong spell requires a great deal of energy, such a from a fire or a flywheel. And thaumaturgy, while rule-based, is not an exact science -- sometimes changes don't stop when they should....
- The Principle of Sympathy: like produces like
- The Principle of Contagion: once together, always together
- The Doctrine of Signatures: the attributes without mirror the powers within
- The Maxim of Persistence: perfection is eternal
- The Rule of Three: thrice spoken, once fulfilled
- Law of Ubiquity: flame permeates all
- Law of Dichotomy: dominance or submission
Alchemy is mostly as you expect it: by properly blending items with the appropriate attributes you can obtain a final product with superior virtues, such as oils of heat resistance or gold from lead. The only problem is that each step of the blending process has a chance of failure -- for example, four out of ten times a particular step in a process might produce lightning or an explosion instead of the intermediate product you actually want. So you have to start with a much larger quantity of initial substances than you wind up with... and the more complex the changes, the more steps are required (and the lower the chance of success on each step).
Hardy's Magic is used to create magical objects. By repeatedly performing rituals of great complexity, common objects can be imbued with properties they can confer to their user. Rings can make their wearer invisible, carpets can fly, glass spheres can give light, and so on. The more perfect the ritual, and the more persistently it is applied, the greater the power of the object. Naturally, if you fail to correctly perform any ritual at any point, the object being given power will probably be destroyed.
Sorcery grants the arts of illusion, of enchantment, of clairvoyance, of fate, and of prophecy. Each of these is activated by speaking a charm three times, which sounds simple enough, but the more complex charms do not want to be said -- each word becomes more difficult to utter. The most complex sorcerous charms are nearly impossible to speak, but must be said without error (and cannot be abandoned once begun). A mistake will produce hallucinations, pain, and even death in the most powerful cases. But even if one succeeds, some amount of one's life force is drained away forever. Cast too great an enchantment with too little life force remaining, and goodbye.
Finally, Wizardry is about summoning and binding demons to your will. Flame is used as a connection to the demon's realm and the Law of Dichotomy requires that there must always be a contest between the summoner and the summoned. Fail to dominate, and the summoned demon will control the summoner.
The nice thing about all these powers is that there's a cost to them. None of the five magics are to be taken lightly, even if you succeed. In a story, that's great for setting up dangers to be overcome; in a computer game, it would be excellent for producing a more thoughtful approach to the application of power. No charging in swinging with these abilities!
Hmm. And maybe right there is the answer why these five styles of magic haven't been used in a new MMORPG....