Brandon Sanderson's Mistborn series is one of my all-time favourite fantasy settings. The world is built around a deconstruction of the classic hero's journey; a thousand years have passed since the prophesied hero - the Hero of Ages - failed in his quest. In this world of red skies where ash periodically falls from the sky like rain and strange mists cloak the streets by night, the Lord Ruler reigns the Final Empire through the noble families with an iron fist. Beneath the nobles are a peasant class known as the Skaa who are treated as little more than slaves. This is the state of the world at the beginning of the series, though things change over the course of the original trilogy and there's a three hundred year timeskip in the fourth book to a steampunk tech level.
Aside from the dark, brooding setting the thing about Mistborn which makes me interested in playing it is the magic system. There are different types of magic in this world, all involving metal in some way or other, but the main one is Allomancy. Allomancers have the ability to ingest and 'burn' certain types of metal to produce a variety of different magical effects depending on the metals used; most Allomancers can only burn one specific type of metal and so have only one power, but a rare few known as 'Mistborn' are able to burn all Allomantic metals for a variety of powers. There's some more to the magic system than that, but those are the basics.
From what little I've heard, the Mistborn Adventure Game itself seems to assume that the players are part of a crew of Mistings (one metal Allomancers) pulling off capers, like Kelsier's band of rogues from the first book. It's been a while since I played a rogue in an ongoing campaign, but they used to be my favoured character type, so I'd love to 'get back to my roots' with this game. I only know of one person at GUGS who has the game, but he hasn't got round to running it yet. All the same, I'd love to have a copy of the book myself, if only to add to my Mistborn collection.