The Mistborn Trilogy by Brandon Sanderson.
Really cool world and concept, the hero of ages was going to save the world from the big scary evil, and faced the temptation of ultimate power that all heroes do and reject. Except this one chose to keep ultimate power. Thousands of years later, the immortal hero rules with an iron first over a dying world. Ash falls from the sky, mist fills the night, priests of the god-king ensure everyone stays in line, and the general populace are slaves to a brutal noble class. The protagonists are a bunch of thieves, hatching a plot to overthrow the hero turned tyrant. Its fantasy meets Oceans 11s
The "magic" system is spiffy, as some people, called allomancers, have the ability to draw power from certain alloys and metals by ingesting and "burning" them. For example, tin allows you to enhance you perception, pewter enhances your strength, steel allows you to pull on other metals etc. Usually if a person can do this, they can only do it for only one of the metals, unless they are the super rare Mistborn, who can use all of them.
