Memories of Ice by Steven Erikson (Malazan Book of the Fallen, book three). I am emotionally exhausted, but in a good way. Take the depth of Tolkien's Middle Earth history, the grit of George RR Martin, and a rolling sword and sorcery pacing and darkness ala Moorcock's early Elric stories, and you have Steven Erikson's style.
Tl;dr synopsis: An empire called the Pannion Domin has declared war. Tenescowri - peasants brainwashed by the Domin and starved to the point of cannibalism - attack cities on Genabackis enmasse. Meanwhile a reincarnated hero to the T'lan Imass (undead neanderthals) raises an army of the Imass to attack the Pannion Domin. To top if off, a malignant entity called the Chained God is attacking the world's warrens, slowly killing the gods and goddesses.