The fourth season of HBO's hit series Game of Thrones just kicked off this past Sunday, but HBO has already ordered two additional seasons of the program. The network made the announcement this morning, with head of programming Michael Lombardo saying that showrunners David Benioff and D.B. Weiss "continue to surpass themselves, and we look forward to more of their dazzling storytelling."

While ordering two seasons at once might seem like a lot, HBO certainly knows where the show will be going. Thrones is based on author George R.R. Martin's A Song of Fire and Ice saga, which currently consists of five novels with two more on the way (eventually). It's not precisely clear which books the new seasons will be based upon, but for season three and four of the program Benioff and Weiss split up the third novel, A Storm of Swords, into two halves. The subsequent volumes in Martin's series, entitled A Feast for Crows and A Dance with Dragons, cover the same time period, but take place in different areas of his fictional world. Benioff and Weiss will likely combine those two novels so fans don't have to go more than a few episodes without seeing their favorite character, but given the massive size of both books splitting them up across multiple seasons is a strong bet. In either case, it's just another sign that the show's popularity is growing — as is the pressure on Martin to finish the series before Benioff and Weiss catch up.