I like the setting/story and the details written therein. The specific light-healing mechanic is great, too. And the idea of fire merchants running around is fun! This would make a great DnD world.

 But with that, I'm a little concerned with the lack of details in the system. It looks like this assumes the GM and/or players know any d20 system. Like, you say AC, but without telling us anything else, we are left to assume that this is supplement that uses a d20 system, but with certain elements replaced. Also, does the pc have no skills? No stats but health and light? It really seems like I'm rolling up a DnD character and playing with this setting in mind, and using fire magic to heal. Even so, I like the setting/story a lot.

i really like the "dune" style light trading

I appreciate the explicit genre reference; saves a lot of words. Other entries would benefit from that approach.