How does this magic system sound?

I have this idea for a magic system for a work I'm writing, and I'd like to know what you guys think.

The basic premise of the system is that, while magic is capable of creating and destroying energy, it cannot do the same to matter.

Because of this, every spell you cast that involves physical matter has to use matter from one's surroundings.

This makes transformation magic functionally impossible, as you have to know exactly what to do with all the matter you need to transform, which is made even more difficult when you realize that, as a living thing, the amount of matter in your body is constantly changing.

The plot revolves around the main character (after being granted magic himself by messing around with a magic artifact) finding a MacGuffin that breaks this rule: the Codex of Creation. The magic contained in it appears to be able to create and destroy both energy and matter, breaking the one known law of magic.

To make things even more complicated, the magic contained within it can't seem to be learned by humans. The only individual that seems capable of using the magic contained in the Codex of Creation is its guardian, a mysterious amnesiac shapeshifter who awakened after the discovery of the Codex, who possesses the ability to transform into a fox at will. As she learns more spells from the Codex, she gains the ability to transform into other animals as well.

Anyway, that's the system of magic that I have outlined. Please tell me what you think!

edited 2nd Aug '11 7:00:41 AM by Zennistrad

It's different and interesting. My only problem with it is, well, matter is energy. Just in a congealed form. Though that could be used as the reason the Codex can apparently break the law.

Okay, so I've decided to set up how the main character, Lawrence, learns magic.

When he arrives at his new home, after moving across the country, the first person he befriends is a girl named Shelly.

Shelly's father is wizard and an archaeologist, and has a large cache of magical knickknacks he has collected from his field work in the attic. When Shelly invites Lawrence to her house, they decide to look at the various things in the attic. Lawrence rather foolishly decides to put on a ring without first trying to find out what it does. The ring melts into his skin and becomes part of his body, and it becomes apparent that the ring's purpose is to permanently give someone who can't use magic the ability to use magic.

Shelly and Lawrence find a strange spellbook in the attic, from Shelly's father's latest field work in the Sahara Desert. It's unlike any spellbook Shelly has seen before, however. Lawrence, again acting foolishly, opens the spellbook, which turns out to be the Codex of Creation mentioned in my previous post. This causes the Codex's guardian to appear, kicking off the main plot...

... That's actually an ingenious idea. I wasn't planning on having the work being 100% scientifically accurate (it does have Functional Magic, after all), but this idea is just too good to pass up. Is it okay if I use it?

edited 2nd Aug '11 6:58:11 AM by Zennistrad

The system is passable (as in, it passes the pass/fail test, but that's an incredibly easy test). The thing is, a huge amount of what makes it good or not is how you work it into your story.

So what you should do is write it, and then ask us what we think.

Feel free to. I wouldn't have shared it if I'd be against anyone using the idea.