El aliento de los dioses / Warbreaker

This is the story of two sisters, the God King one of them has to marry, the lesser god who doesn't like his job, and the immortal who's still trying to undo the mistakes he made years ago. Their world is one in which those who die in glory return as gods to live confined to a pantheon in Hallandren's capital city and where a power magic is based on an essence that can only be collected one unit at a time from individual people.