So this book series right now, has no ending? So how long before the TV series catches up to where the books are? Then what happens?
There are supposed to be 7 books. Five have been published. We'll see if the author actually finishes the last two before the series catches up.
The series is up to roughly 60% of the way through book 3. Season 4 will be the rest of book 3 and into book 4.