Stannis is alive in the books.

via Salon:

While we never exactly saw Stannis Baratheon die on the show, we did see him get a sword to the head courtesy of Brienne of Tarth before the camera cut away, making it seem pretty clear that the disgraced Lord of Dragonstone was well on his way to a rendezvous with the Many Faced God. As episode director David Nutter said at Comic-Con, “From the beginning, and [through] the script process, that was the intent — he’s dead.”

But according to George R. R Martin, Stannis is alive and well — at least in the books. At the end of “A Dance With Dragons”, Ramsay Bolton sends a letter to Jon Snow saying he has killed Stannis, even though we never witness the actual death take place. But addressing a fan on his LiveJournal who asked whether Stannis was alive or dead, Martin responded definitively: “In my books? Alive beyond a doubt.”

Of course, the books and the show often diverge (remember the whole Lady Stoneheart debacle?) so it’s possible that Stannis is alive in the books and dead in the show. Or it is possible that Stannis somehow survived Brienne’s sword and he has a part to play in the great (onscreen) battle of ice and fire to come. But most importantly, it leaves open the option that Book-Stannis could be redeemed as a character — which would be a nice consolation prize for the fans still reeling from TV-Stannis’ arc at the end of last season.