The Sworn is fifth in Martin's Winter Kingdom world. World. Not series. The first four books that take place in the Winter Kingdoms are part of the Chronicles of the Necromancer. The Sworn revisits those characters and the setting, but begins the new Fallen Kings Cycle.
Normally I wouldn't have jumped into this willy nilly. I'm a preparer. I like to have all the previous books down before I start a new title if I know that it's a continuation or part of an official series. But, Martin moved to Orbit for this one and I wasn't entirely sure until I started it that it was not the first in a unique series. Fortunately, true to the extras in the back of the book (and this post from the Orbit site), The Sworn is set up in a way that even a newbie like me can jump in without being lost. (A warning, though, the prologue to the book set me in the wrong direction. I know, I know. It's meant to catch readers up to speed, but it threw me off completely. If you're like me, though, trust me when I say you'll get it. It will make sense later.)
The Sworn begins six months after Chronicles of the Necromancer ends. Peace is not in the cards for the Winter Kingdoms. Signs point to war on the horizon, a War of Unmaking. A dark force that has been sleeping threatens to awaken and rise again and an enemy of the Winter Kingdoms would raise the dead as his army.
True to epic fantasy form, there are a ton of characters and subplots for almost each of them. It's clear that each is connected, some from the previous books and some yet to be brought together. The only way to sum it up easily for you here is obviously cryptic and I do apologize for that. Can't be helped, though. It's an intricately plotted story and a picture of amazing world building.
Ah. I loved it. Martin's Winter Kingdoms are filled with vampires and werewolves and magic and ghosts. I can't wait to find out what happens next. Fortunately, I have four books to go back to in the meantime : )
Chronicles of the Necromancer:
The Blood King
Dark Lady's Chosen
The Fallen Kings Cycle:
The Dread (2012?)