You would be hard-pressed right now to find an author with a more eagerly -awaited next installment than George R. R. Martin with Winds of Winter.
This follow-up to the hugely successful Song of Ice and Fire (a continuance of the series upon which Game of Thrones is based) was anticipated by year-end, and now the TV series is about to catch up to the book series.
It would be completely unprecedented to have the TV show “spoiling” the books, but since the plot has to advance and the book won’t be out before it does, it’s likely to happen on some level.
He missed his deadline. Twice. And because he felt that the product he was rushing to produce wasn’t good enough to go to print.