From the description at amazon.com:

Fresh from the success of The Way of Kings, Brandon Sanderson, best known for completing Robert Jordan's Wheel of Time®, takes a break to return to the world of the bestselling Mistborn series.

Three hundred years after the events of the Mistborn trilogy, Scadrial is now on the verge of modernity, with railroads to supplement the canals, electric lighting in the streets and the homes of the wealthy, and the first steel-framed skyscrapers racing for the clouds.

Kelsier, Vin, Elend, Sazed, Spook, and the rest are now part of history--or religion. Yet even as science and technology are reaching new heights, the old magics of Allomancy and Feruchemy continue to play a role in this reborn world. Out in the frontier lands known as the Roughs, they are crucial tools for the brave men and women attempting to establish order and justice.

One such is Waxillium Ladrian, a rare Twinborn, who can Push on metals with his Allomancy and use Feruchemy to become lighter or heavier at will. After twenty years in the Roughs, Wax has been forced by family tragedy to return to the metropolis of Elendel. Now he must reluctantly put away his guns and assume the duties and dignity incumbent upon the head of a noble house. Or so he thinks, until he learns the hard way that the mansions and elegant tree-lined streets of the city can be even more dangerous than the dusty plains of the Roughs.

From amazon.com:

From #1 New York Times bestselling author Brandon Sanderson, the Mistborn series is a heist story of political intrigue and magical, martial-arts action.

Three hundred years after the events of the Mistborn trilogy, Scadrial is now on the verge of modernity, with railroads to supplement the canals, electric lighting in the streets and the homes of the wealthy, and the first steel-framed skyscrapers racing for the clouds.

When family obligations forced Waxillium Ladrian to forsake the frontier lands and return to the metropolis of his birth to take his place as head of a noble House, he little imagined that the crime-fighting skills acquired during twenty years in the dusty plains would be just as applicable in the big city. He soon learned that there too, just being a talented Twinborn — one who can use both Allomancy and Feruchemy, the dominant magical modes on Scadrial — would not suffice.

This bustling, optimistic, but still shaky society will now face its first test by terrorism and assassination, crimes intended to stir up labor strife and religious conflict. Wax, his eccentric sidekick Wayne, and brilliant, beautiful young Marasi, now officially part of the constabulary, must unravel the conspiracy before civil strife can stop Scadrial’s progress in its tracks.

From amazon.com:

From #1 New York Times bestselling author Brandon Sanderson, the Mistborn series is a heist story of political intrigue and magical, martial-arts action.

Three hundred years after the events of the Mistborn trilogy, Scadrial is now on the verge of modernity, with railroads to supplement the canals, electric lighting in the streets and the homes of the wealthy, and the first steel-framed skyscrapers racing for the clouds.

The Bands of Mourning are the mythical metal minds owned by the Lord Ruler, said to grant anyone who wears them the powers that the Lord Ruler had at his command. Hardly anyone thinks they really exist. A kandra researcher has returned to Elendel with images that seem to depict the Bands, as well as writings in a language that no one can read. Waxillium Ladrian is recruited to travel south to the city of New Seran to investigate. Along the way he discovers hints that point to the true goals of his uncle Edwarn and the shadowy organization known as The Set.