What The Burning of Shireen Tells Us About Stannis Future

One of the most shocking moments at the end of game of thrones was the burning of Shireen Baratheon by her father Stannis and her mother Selyse. Many fans believed there is no way George RR Martin's version of Stannis would do this, until GRRM told us directly that Stannis would make this decision, so what does that mean for Stannis story in the future of the books? What will have to happen for him to end up in such a desperate situation? When and how will this happen?