I was a latecomer to George R.R. Martin's "A Song of Ice and Fire" (aka A Game of Thrones series). ...
... I am now in the position that those earlier adopters are in, which is the seemingly endless wait for Martin to finish the sixth novel, which is supposed to be titled The Winds of Winter. I gather that part of the reason for the long waits before publication of the last two books was that Martin had found the plot getting away from him and ending up twisted into some tight conundrums that he had to figure out how to unravel. That's not surprising, considering how many characters there are and how many plot lines.
He's a man with a plan. Check it out.